CHAPTER-V RESULTS & DISCUSSIONshodhganga.inflibnet.ac.in/bitstream/10603/6525/10/10_chapter...

CHAPTER-V

RESULTS & DISCUSSION

The present research was conducted to study whether the use of subliminal stimuli

could be used as a deterrent to countermeasures in lie detection. The objectives of

the study have been presented in Chapter III. Present study was conducted in three

phases. In Phase I of the study, 10 neutral words were presented to each subject and

the exposure time / word was varied across 3 levels (Group I: 0.5sec.; Group II:

0.01sec.; Group III: 0.001 sec.) in order to determine the subliminal subjective

threshold (70% detection) in terms of the accuracy of recognition of the word. In

order to determine whether nature of stimuli (subliminal/supraliminal) led to

variation in physiological arousal (GSR), a sample of 10 subjects were shown 10

words ((4 subliminal, 6 supraliminal) and their GSR was recorded (baseline as well

as during the presentation). Then the GSR (skin resistance) score of each subject for

each word (subliminal/supraliminal) was calculated.

In Phase II, each subject underwent a pre-training session where two neutral stimuli

were made aversive, for which subjects underwent a classical conditioning session

where two neutral stimuli were paired with electric shock (10 volt to 18.2 volt). The

investigator could have used negatively toned words but since the degree of negative

affect would have varied across subjects, it was decided that neutral words would

be made aversive by paring them with a negative stimuli(electric shock) so that inter

subject variation could be controlled. During experimentation, a group of 28 subjects

were presented with 10 stimuli (3 aversive: 2 subliminal and 1 supraliminal + 7

neutral: 5 supraliminal and 2 subliminal) and physiological arousal (GSR) was

recorded (baseline as well as during the presentation period).

In Phase III, subjects were trained for using countermeasures i.e. to give fake

responses in order to increase their arousal level. For physical countermeasure, toe

to the floor was used while for mental countermeasure, counting backward by 7 was

used. Twenty two subjects were give training for countermeasures (Physical

Results & Discussion

91

countermeasures (n=11) and mental countermeasures (n=11) and same procedure as

in Phase II was repeated, except that now the subjects were instructed to use the

countermeasures whenever a neutral stimuli was presented.

Data Transformation and Analysis

In order to achieve the objectives of the present study, ongoing graphical recording

of GSR of every subject was obtained during the presentation period and saved in lie

detector and later a hard copy was obtained. After completion of the experimentation

the graphical recording was scaled into scores. Eleven values of GSR (skin

resistance) were computed for each subject i.e. one baseline and 10 scores, i.e. in

response to the 10 stimuli, were obtained. Then, resistance (kilo ohms) scores were

converted into conductance (micro ohms) scores by using the formula C=1/R. As

GSR is a very sensitive index and tends to fluctuation intra (situational variation) as

well as inter individually, it is recommended that each observation should be

estimated in terms of variation from the baseline level. Also, through skin resistance

(in terms of raw ohms) is technically easier to measure, there is evidence that

conductance is a better measure of physiological arousal (Edelberg, 1972).

Since the scores were in micro ohms each conductance score was multiplied with

100 in order to remove the two zeros after the decimal. Then, the deviation of each

of the conductance score, from the respective baseline, was computed. Since some

of the values were negative, a constant value (130) was added to each of the

deviation (d) scores so that all scores were made positive. This statistically

converted score was taken as an index of physiological arousal in response to the

specific stimuli, measured in term of GSR, for the present study.

Single group, repeated measure (across stimuli)/multi group design experiments

were used to meet the objectives of the present study, therefore for analyses of the

data, descriptive statistics, Friedman Test (non-parametric) followed by Wilcoxon

Signed-Rank Test (non-parametric) or one way ANOVA followed by post hoc test,

were applied. Non-parametric analysis was opted for the analysis of the single group

design experiments as the assumptions of homogeneity and normalcy (sample was


92

small) could not be fulfilled by the data and therefore parametric analysis could not

be applied (Conover, 1980). The data were analyzed using the Predictive analytics

Software (PASW) 18.0 version for Window Inc., Chicago, Illinois, USA. The

statistical significance level was considered at p ≤ 0.05.

Phase – I

The objective of this Phase was to determine whether physiological arousal would

vary in response to subliminal and supraliminal stimuli. Initially the recognition

scores of 30 subjects (three group, n=10) were considered in order to ensure that the

variation in the nature of stimulus (font color and exposure time) led to

supraliminal/subliminal presentation. The recognition scores of the three groups

have been presented in Table 5.1

Table 5.1. Number of correct recognition during presentation of 10 stimuli for

varying exposure intervals.

Sr. No. Group I

(0.5 sec.)

Group II

(0.01 sec.)

Group III

(0.001 sec.)

1 10 8 7

2 10 8 6

3 10 8 7

4 10 8 6

5 10 8 6

6 10 8 6

7 10 8 7

8 10 8 7

9 10 8 6

10 10 8 7

Mean 10 8 6.5

From the means it is evident that an exposure period of 0.5 sec (light yellow

stimulus on white background) elicited a recognition response on all trials (100%).

Reduction in the exposure time (0.01) led to a subsequent reduction in the


93

recognition score (80%).Further reduction in the exposures time (0.001) led to a

further reduction in the mean recognition score(65%).

The significance of difference among the mean recognition scores of these three

groups was analyzed by applying one way ANOVA followed by post hoc analyses

(Scheffe).

Table 5.2. Significance of difference among the mean recognition scores of the

three groups.

Source of variance Sum of Squares df Mean Square F

Between Groups 61.67 2 30.83 333.00

Within Groups 2.500 27 .093

Total 64.17 29

p< 0.01

The obtained value of F was found to be significant beyond the 0.01 level, therefore

the difference between the mean recognition scores of the three groups were

analyzed by applying Scheffe’s test.

Table 5.3. Significance of difference between the mean recognition scores of the

three groups.

Group Comparison groups Mean Difference

Group I (0.5 sec.) II 2.00000*

III 3.50000*

Group II (0.01 sec.) I -2.00000*

III 1.50000*

Group III (0.001 sec.) I -3.50000*

II -1.50000*

p<0.01

The post hoc analysis revealed that all the three recognition means were

significantly different from each other. The detection of words was 100% for the

highest exposure time (0.5 sec.), 80% for .01 sec. and 65% for .001 sec. The present

investigator had decided to use a 70% detection level as the subjective subliminal

threshold. Detection (recognition) of stimuli during the shortest presentation period


94

(0.001 sec.) was 7 for five subjects and 6 for the remaining five (mean: 6.5).Since

during the pilot work, use of exposure intervals of more than 0.001 sec. had led to

80% detection in some of the subjects, it was decided that an interval of 0.001 sec

would be used as the exposure interval for subliminal level presentation, in order to

ensure that detection should not exceed 70% for any subject. Some earlier

researchers have used brief exposure intervals for subliminal presentation e.g. Victor

(2009) 250 m.sec, Masling, et al. (1991) 4 m sec., Kunst-Wilson and Zajonc (1980)

1 m sec. and Lazarus and McCleary (1951) 1 m.sec. to 6 msec. These researches

provide support for selection of the exposure time (.001 sec.) for subliminal in the

present research. However, the stimulus was in the form of a message in majority of

these researches, thereby justifying longer time intervals. In the present study as the

stimulus was a single word, with maximum 7 alphabets, presented in font size 66” in

light yellow font color, on a white background, therefore, a shorter interval was

found to be required for subliminal (subjective threshold) presentation. Thus, for the

present investigation, 0.001 sec. was used as the exposure time for subliminal and

0.5 sec. for supraliminal presentation.

In order determine whether physiological arousal would vary in response to stimuli

presented at these subliminal and supraliminal exposure intervals, a group of ten

subjects were presented with ten neutral words and their GSR was recorded.

Assessment of GSR in response to Neutral Stimuli

In order to determine the variation in GSR in response to subliminal and

supraliminal stimuli, a sample of 10 subjects were shown 10 words (4 subliminal, 6

supraliminal) and their GSR was recorded. After recording the GSR, baselines as

well as GSR resistance scores in response to the 10 words (subliminal/supraliminal)

were calculated for each subject from the graphical recording. Then, the statistically

converted GSR score of 10 subjects in response to the 10 neutral stimuli (subliminal

and supraliminal) were computed. These have been tabulated in Table 5.4.


95

Table 5.4. GSR scores in response to Neutral Stimuli.

Sr.

No

S1

Sup

S2

Sup

S3

Sub

S4

Sup

S5

Sub

S6

Sup

S7

Sub

S8

Sup

S9

Sub

S10

Sup

1 155 183 160 140 135 140 135 145 126 155

2 120 120 150 140 150 140 120 150 102 130

3 143 184 170 156 143 156 170 156 156 170

4 102 255 190 130 102 102 159 159 144 144

5 160 116 102 306 246 228 228 210 210 176

6 128 126 124 122 125 123 121 124 117 119

7 147 147 115 85 85 71 57 57 57 64

8 145 192 152 117 85 79 79 73 73 97

9 174 159 144 137 123 137 197 166 189 151

10 139 148 130 129 144 106 141 137 133 105

Perusal of the individual GSR scores shows that the scores for the first stimulus (S1,

supraliminal) were lower (except for sub. no, 5, 6, and 9) as compare to second

supraliminal stimulus (S2). On the next stimulus (S3 subliminal), GSR of all subjects

(except for sub. no. 2) decreased as compare to second supraliminal stimulus. Next

word in the presentation (S4) was a supraliminal stimulus and GSR scores for this

stimulus were surprisingly lower than the previous subliminal stimuli (except for

sub. no 5). The reason could be attributed to the fact that the preceding GSR was

lower and the effect of the succeeding stimulus was confounded with the response

given to the preceding stimulus. The next neutral stimulus (S5) was subliminal and

GSR scores for this stimulus were also lower (except for sub. no. 2, 10) as compared

to previous supraliminal stimuli (S4). The sixth stimulus (S6) was supraliminal and

GSR scores for this stimulus were also lower (except for sub. no. 1, 3, and 9) as

compared to previous subliminal stimulus (S5).The next stimulus (S7) was

subliminal and GSR scores for this stimulus were also lower (except for sub. no. 3,

4, 9, and 10) as compared to previous supraliminal stimulus (S6). The eighth

stimulus (S8 supraliminal) again elicited a lower GSR (except for sub. no. 1, 2, 6) as

compared to previous subliminal stimulus (S7). The ninth stimulus, which was

subliminal (S9), had a yet lower (except for sub. no. 9) GSR score as compared to

the previous supraliminal stimulus (S8). The last stimulus (S10) in the presentation


96

was supraliminal and GSR scores for this stimulus were higher (except for sub. no.

5, 9, and 10) as compared to previous subliminal stimulus (S9).

Thus, in the entire presentation, total 40 neutral stimuli were presented to all the 10

subjects (4 stimuli × 10 subjects) in subliminal form, where GSR was found to be

lower than the preceding stimulus on 24 presentations as compared to supraliminal

stimuli. Since in the present study the subliminal threshold (subjective) was consider

as 65% detection level, the experimenter had expected a lower GSR on minimum

35% trials. Thus, from Table 5.4, it can be concluded that GSR of the subjects is

lower in response to subliminal stimulus as compared to the supraliminal stimuli. In

order to analyses the data statistically, descriptive statistics (Mean & SD) were

computed for each of the stimulus.

Table 5. 5. Mean and SD of GSR scores in response to Neutral Stimuli.

Neutral Words Mean SD Mean Rank

Supra(S1) 141.30 20.6 5.95

Supra(S2) 163.00 42.2 7.95

Sub(S3) 143.70 26.5 6.75

Supra(S4) 146.20 59.2 5.25

Sub(S5) 133.80 45.9 5.35

Supra(S6) 128.20 44.7 4.30

Sub(S7) 140.70 51.2 5.50

Supra(S8) 137.70 44.6 5.55

Sub(S9) 130.70 47.4 3.60

Supra(S10) 131.10 35.2 4.80

From Table 5.5 it can be seen that the supraliminally presented neutral words had a

higher mean GSR score as compared to subliminal stimuli. Highest mean score on

supraliminal level was 163 while the lowest value at this level is 128.2. On the other

side the highest mean value on subliminal level was 143 while the lowest mean

value is 130.7.

Mean GSR scores in response to the subliminal/supraliminal stimuli have been

depicted in Figure 5.1

Figure-5.1. Mean GSR scores in response to Neutral Stimuli

From the Figure 5.1, it is clearly evident that the mean GSR scores did not vary

much except for the second stimulus. The mean scores for supraliminal stimuli and

subliminal stimuli appear to be equal (except 2

appears that use of mean values while evaluating the effect of stimulus exposure on

GSR can be misleading when summated

In order to determine whether the difference a

the neutral stimuli was statistically significant, Friedman test was applied

indicated that there was no

subliminal or supraliminal stimuli (

fail to verify the first hypothesis which predicted

responses to supraliminal neutral stimuli would be more intense as compared to

subliminal neutral stimuli.

The present results reveal that, when

to neutral words presented either at subliminal/supraliminal level do not vary

significantly. However, the individual GSR scores evinced a lower score against

subliminal stimuli as compared to supraliminal sti

presentations. Thus, the present results indicate that pooling GSR values across

0

20

40

60

80

100

120

140

160

180

S1 S2 S3

GSR


97

Mean GSR scores in response to Neutral Stimuli



stimuli appear to be equal (except 2nd

supraliminal stimuli).


when summated across subjects.

In order to determine whether the difference among the GSR scores in response to

the neutral stimuli was statistically significant, Friedman test was applied. Analysis

there was no-difference in GSR in response to either neutral

subliminal or supraliminal stimuli ( χ2 (9) = 15.02, p = .09). Thus, the present results

fail to verify the first hypothesis which predicted that physiological arousal


The present results reveal that, when pooled across subjects, GSR scores in response



subliminal stimuli as compared to supraliminal stimuli on more than 50% of the


S4 S5 S6 S7 S8 S9 S10

Stimulus Number




supraliminal stimuli). Also, it


mong the GSR scores in response to

. Analysis

GSR in response to either neutral

Thus, the present results

physiological arousal


pooled across subjects, GSR scores in response



muli on more than 50% of the


Supra

Sub


98

subjects can be misleading and intra subject variations should also be considered.

However, the present results clearly show that the mean GSR score was more than

the baseline score for 3 of the subliminal stimuli and the variation in response to the

subliminal stimuli was not found to be significantly different from the response to

the supraliminal stimuli. Thus, it can be inferred that even though the subliminal

stimuli were below the subjective threshold, they did elicit a substantial

physiological arousal.

Subliminal perception is the phenomenon of responding to stimuli below the

awareness threshold (Dixon, 1981). It occurs when stimuli of low intensity or short

duration or at frequencies beyond the normal range for conscious perception are

presented. Signal to noise ratio for achieving “perception without awareness” may

also be brought about by masking or by presenting stimuli in sensory channels that

may not be currently mediating conscious perception. The theory that subliminal

perception occurs when external stimulation is too weak or brief to produce

sufficient activation of the reticular system is supported by the research findings of

Libet, Alberts and Feinstein (1967). Dixon (1981) had also shown that visually

evoked responses, galvanic skin response, verbal behavior, conscious perception of

supraliminal stimulus arrays, and even dreams may be partially cued by the meaning

of verbal and pictorial stimuli presented below the awareness threshold.

The present results receive support from the findings of McCleary and Lazarus

(1949) and Lazarus and McCleary (1951) who presented five-letter nonsense

syllables to subjects, flashed at speeds ranging from 6 ms to one second, on a screen

placed seven feet from the subject and measured electrodermal responses (EDRs).

They demonstrated that subjects were able to make discriminatory responses to

stimuli presented at speeds which were too rapid for conscious recognition. More

recently, Masling, Bornstein, Poynton, Reed, and Katkin (1991), using an arousing

experimental message (NO ONE LOVES ME) and a neutral control message (NO

ONE LIFTS IT) found that subjects exposed to the short duration (4 ms) arousing

message showed a significant increase in EDR when compared to controls. These

results provide support for the fact that stimuli presented below awareness

thresholds (subliminal level) produce significant effect on skin resistance response.


99

Considered together the results of the Phase I show that a short exposure interval

reduces the probability of conscious processing of discrete stimuli. Further, the

variation in skin conductance (GSR) in response to subliminal (subjective threshold)

stimuli is comparable to that of supraliminal stimuli, especially when pooled across

a group of subject. Since, in the present investigation, for the subliminal stimuli, the

delectability varied from 60 to 70%, it is probable that a particular subliminal stimuli

which did not transgress conscious awareness on one presentation, might do so at

another (intra as well as inter subject variation). Thus, pooling of the GSR scores

across subjects, for computation of mean GSR in response to a particular stimulus

confounded the results.

Phase II

The objective of this Phase was to study the quantitative differences in physiological

response (galvanic skin response-GSR) to supraliminal and subliminal stimulation.

The baseline GSR resistance score for each subject and the resistance score for the 7

neutral and 3 aversive stimuli (subliminal/supraliminal) were calculated from the

graphical recording of GSR. Table 5.6 shows the statistically converted GSR score

of 28 subjects in response to 10 stimuli (subliminal / supraliminal and

aversive/neutral).

Three aversive and seven neutral stimuli were presented to each subject. Among the

aversive stimuli, two were subliminal (S3 and S9) while one was supraliminal (S6).

From Table 5.6 it can be seen that a number of subjects (i.e. sr. no, 1, 2, 3, 4, 5, 6, 7,

8, 12, 14, 15) had a higher GSR score in response to the aversive stimuli as compare

to neutral stimuli. However, a few subjects (i.e. sr. no. 9,10,13,24 etc.) showed

higher GSR for the neutral stimuli as compared to the aversive stimuli. Perusal of

the individual GSR score shows that for the first subliminal aversive stimulus (S3)

GSR was higher (except for sub. no, 9, 10, 13) as compared to the preceding neutral

supraliminal stimulus (S2). Next aversive stimuli in the presentation was

supraliminal and GSR in response to this stimulus (S6) was higher than the previous

supraliminal neutral stimulus (except for sub. no 7, 16). The next aversive stimulus


100

Table 5.6. GSR scores in response to Neutral and Aversive stimuli.

Sr.No Stimulus Number

S1 Sup-N

S2

Sup-N

S3

Sub-A

S4

Sup-N

S5

Sub-N

S6

Sup-A

S7

Sub-N

S8

Sup-N

S9

Sub-A

S10

Sup-N

1 136 146 168 165 160 176 164 166 171 150

2 125 145 167 137 147 185 157 152 198 152

3 155 206 271 196 226 242 211 265 253 289

4 132 155 212 178 184 241 203 209 256 213

5 138 143 168 157 155 184 152 149 185 148

6 132 129 182 144 149 158 145 144 198 142

7 195 195 240 174 181 141 106 118 278 130

8 152 160 169 138 150 196 117 111 189 105

9 139 149 145 145 168 178 148 140 160 162

10 128 128 126 125 125 143 122 119 174 119

11 126 124 132 139 130 138 121 119 135 126

12 130 134 136 134 136 164 134 134 138 138

13 140 158 148 147 148 178 142 129 165 160

14 134 134 135 135 136 142 134 135 134 134

15 129 135 135 142 134 147 137 135 141 141

16 127 125 245 122 219 139 120 129 245 123

17 122 120 117 112 105 178 115 120 146 164

18 128 137 138 120 123 149 126 131 147 132

19 123 106 154 114 95 148 101 89 148 92

20 129 131 131 144 134 149 116 119 145 113

21 137 137 138 141 142 148 143 141 137 136

22 154 96 254 10 65 214 142 75 224 242

23 199 247 264 184 156 248 87 255 247 163

24 135 134 129 126 133 147 134 131 128 131

25 128 127 126 127 123 135 125 122 125 122

26 149 156 258 235 238 269 245 250 253 248

27 126 115 298 186 258 228 201 181 254 167

28 222 222 312 102 76 260 257 257 259 257

Mean 141.7 146.2 182.07 142.1 149.86 179.4 146.6 150.8 186.8 157.1

was again subliminal and GSR score for this stimulus (S9) was also higher than the

previous supraliminal neutral (S8) stimulus (except for sub. no 14, 24).

The mean GSR scores in response to each of the stimuli were computed. From the

means it can be seen that all three aversive stimulus had higher GSR as compared to

neutral stimuli irrespective of whether they were presented at supraliminal or

subliminal level. The mean GSR scores have been depicted in Figure 5.2

Figure-5.2. Mean GSR scores in response to Aversion and Neutral Stimuli.

Figure 5.2 presents a clear picture of the physiological arousal against aversive and

neutral stimuli when presented either in supraliminal and subliminal form. The line

graph showing a progressive increase in means GSR whenever an aversive stimulus

is presented. For each aversive stimulus, there is a higher GSR mean score as

compared to neutral stimuli whether presented in subliminal or supraliminal form.

On the basis of mean GSR

higher GSR response as compared

In the present investigation the stimuli had been varied in two ways i.e. nature of

presentation: subliminal/supraliminal and nature of stimuli: neutral/aversive. The

data were statistically analyzed in four separate ways in order to

effect of subliminal presentation of aversive stimuli on GSR.

Assessment of GSR for subliminal stimuli

Mean GSR scores for subliminally presented aversive and neutral

presented in Table 5.7. From the table it evident that the aversive

mean GSR scores as compared to neutral stimuli.

0

20

40

60

80

100

120

140

160

180

200

S1 S2 S3

GSR


101

2. Mean GSR scores in response to Aversion and Neutral Stimuli.

presents a clear picture of the physiological arousal against aversive and



each aversive stimulus, there is a higher GSR mean score as


On the basis of mean GSR scores it can be concluded that all aversive stimuli had

higher GSR response as compared to neutral stimuli.



data were statistically analyzed in four separate ways in order to understand the

effect of subliminal presentation of aversive stimuli on GSR.


Mean GSR scores for subliminally presented aversive and neutral stimuli have

presented in Table 5.7. From the table it evident that the aversive stimuli had

mean GSR scores as compared to neutral stimuli.

S4 S5 S6 S7 S8 S9

Stimulus Number


2. Mean GSR scores in response to Aversion and Neutral Stimuli.

presents a clear picture of the physiological arousal against aversive and



each aversive stimulus, there is a higher GSR mean score as


can be concluded that all aversive stimuli had



understand the

stimuli have been

stimuli had higher

S10

Aversive

Neutral

Table 5.7. Mean and SD of the GSR

Nature of Stimuli

A(S3)

N(S5)

N(S7)

A(S9)

The mean GSR score for first aversive stimulus

aversive stimuli (S9) had a score of 186.89. Neutral subliminal stimuli

had a lower mean score as compared to aversive stimuli. The mean score of first

neutral subliminal stimulus (S

had a mean value of 146.89. These mean values have been depicted in Figure 5.3

Figure 5.3. Mean of GSR scores in response to subliminal stimuli.

From the Figure 5.3, it is clear that GSR for aversive subliminal stimuli was higher

in comparison to neutral subliminal stimuli.

In order to determine whether the difference among the

subliminal stimuli was statistically significant, Friedman Test was applied.

0

20

40

60

80

100

120

140

160

180

200

S3

GSR


102

Mean and SD of the GSR scores in response to subliminal stimuli.

Mean SD Mean Rank

182.07 59.96 3.05

149.86 44.74 1.93

146.61 41.35 1.71

186.89 50.21 3.30

The mean GSR score for first aversive stimulus (S3) was 182.07 while the second

had a score of 186.89. Neutral subliminal stimuli (S5


neutral subliminal stimulus (S5) was 149.61 and the second neutral stimulus (S7)


Mean of GSR scores in response to subliminal stimuli.


in comparison to neutral subliminal stimuli.


subliminal stimuli was statistically significant, Friedman Test was applied.

S5 S7 S9

Stimulus Number


response to subliminal stimuli.

Mean Rank

3.05

1.93

1.71

3.30

was 182.07 while the second

5 and S7)


) was 149.61 and the second neutral stimulus (S7)



response to

subliminal stimuli was statistically significant, Friedman Test was applied. Analysis

Neutral

Aversive


103

revealed that there was a statistically significance difference in mean GSR among

the subliminal stimuli (χ2 (3) = 32.43, p = .000).

The differences between the mean GSR scores of the various stimuli were analyzed

by applying Wilcoxon Test (non-parametric).

Table-5.8. Significance of difference between the GSR scores of the four

subliminal stimuli.

Comparisons

between NS5-AS3 N S7-A S3 A S3-A S9 A S9-N S5 A S9-N S7

N S5-N S7

Z score -3.481 -3.963 -1.322 -4.009 -4.230 -1.654

P .001 .000 .186 .000 .000 .196

From Table 5.8, it can be seen that the mean GSR scores of all the pairs with neutral

vs aversive stimuli where found to be significantly different from each other and the

scores of the aversive stimuli were higher. However, no significance differences

were observed between the GSR scores in response to similar stimuli i.e. for neutral-

neutral and aversive-aversive the comparisons between the GSR scores were not

significant. The results confirm the fact that the GSR level is significantly higher for

subliminal aversive stimuli as compared to neutral stimuli.

These results receive support form an earlier study by Kotze and Moller (1990)

where emotional and neutral words were presented subliminally to healthy subjects.

Their results showed a significant increase in GSR response for emotional but not

for neutral words. In another study by Kostandov and Arzumanov(1986) , P300

component of the evoked potential was recorded over both hemispheres in order to

study inter hemispheric differences in the process of perception of subliminal verbal

stimuli. The stimuli were subliminal words, neutral and emotional, presented at

random to the left or right visual fields. In response to an unrecognized emotional

word, the amplitude of P300 wave increased diffusely over both hemispheres as

compared to that to a neutral word, with no charges in inter hemispheric differences.

The inter hemispheric difference changed considerably in the presence of an

unaccountable emotion caused by a subliminal word. This suggests unilateral

activation of the right hemisphere and a predominant role of this hemisphere in the


104

cortical organization of the unconscious function 'unaccountable emotion.’

Subliminal emotional words, connected with the subject's conflict situation, evoke a

P300 of significantly larger amplitude than subliminal neutral words. The increase

was generalized over occipital and associative areas, and at the cortex.

On the basis of the present results, it can be concluded that physiological arousal is

higher for the aversive stimuli as compared to neutral stimuli, when presented in

subliminal form.

Assessment of GSR in response supraliminal stimuli

The investigator had presented 6 stimuli at supraliminal level, where 5 were neutral

and one was aversive. From Table, 5.6, it can be seem that a large number of

subjects (i.e. sr. no, 1, 2, 8, 12, 14, 15, 19, 20, 24, 25, 26, 28) had high GSR on

aversive stimuli as compare to neutral stimuli presented at supraliminal level.

However, some subjects (i.e. sr. no. 9, 10,13,22,27 etc.) showed high GSR for the

neutral stimuli as compare to aversive stimuli.

Mean values of GSR for aversive and neutral, supraliminally presented stimuli have

been shown in Table 5.9.

Table 5.9. Mean and SD of GSR scores in response to supraliminal stimuli.

Supraliminal Mean SD Mean Rank

N(S1) 141.78 24.47 2.66

N(S2) 146.21 33.93 3.05

N(S4) 142.10 38.92 3.14

A(S6) 179.46 41.71 5.71

N(S8) 150.89 50.68 3.18

N(S10) 157.10 48.66 3.25

From the Table 5.9 it can be seen that the aversive stimuli had a substantially higher

mean GSR score as compared to neutral stimuli when all stimuli were presented at

supraliminal level. The mean value of aversive stimuli is 179.4. All neutral

supraliminal stimuli showed a

stimuli. The mean score of first neutral words (S

word (S2) has mean value of 146.21. Fourth

stimuli also had lower mean score as compare to the aversive stimuli.

values have been depicted in Figure 5.4.

Figure 5.4. Mean GSR scores in response to supraliminal

Figure 5.4 presents a clear picture of the physiological arousal in response to

the aversive and neutral, supraliminal stimuli in term of mean values of GSR score.

The line graph shows that GSR is nearly simila

clearly higher for the aversive stimuli. Thus, it appears that for the aversive stimuli

GSR is higher as compared to neutral stimuli when presented supraliminally.

In order to determine whether the difference among the

the six supraliminal stimuli was statistically significant, Friedman Test was applied

Analysis revealed that there was a statistically significance

mean GSR scores for the supraliminal stimuli. (

The differences between the mean GSR scores in response to the various

supraliminal stimuli were analyzed by applying

0

20

40

60

80

100

120

140

160

180

200

S1 S2

GSR


105

ed a lower mean GSR score as compared to the aversive

re of first neutral words (S1) is 141.78 and second neutral

mean value of 146.21. Fourth (S4), Fifth (S8) and sixth (S10

stimuli also had lower mean score as compare to the aversive stimuli. These mean

values have been depicted in Figure 5.4.

scores in response to supraliminal stimuli.

presents a clear picture of the physiological arousal in response to


The line graph shows that GSR is nearly similar for neutral stimuli whereas it is




the six supraliminal stimuli was statistically significant, Friedman Test was applied

Analysis revealed that there was a statistically significance difference among the

mean GSR scores for the supraliminal stimuli. (χ2 (5) = 50.02, p= .000)


supraliminal stimuli were analyzed by applying Wilcoxon Test (non-parametric).

S4 S6 S8 S10

Stimulus Number


as compared to the aversive

and second neutral

10) neutral

These mean

presents a clear picture of the physiological arousal in response to


r for neutral stimuli whereas it is



response to

the six supraliminal stimuli was statistically significant, Friedman Test was applied.

among the


parametric).

Aversive

Neutral


106

Significance of difference between the mean GSR score in response to the aversive

stimulus with that in response to the neutral stimuli have been shown in Table 5.10

Table 5.10. Significance of difference between the GSR score of the

supraliminally presented aversive stimuli with the neutral stimuli.

Supraliminal (AS6-NS1) (AS6-NS2) (A S6-N4) (A S6-NS8) (A S6-NS10)

Z score -4.145 -4.100 -4.225 -4.225 -3.634

p .000 .000 .000 .000 .000

From Table 5.10, it can be seems that the difference between the mean GSR scores,

for all pairs of neutral and aversive stimuli, were significantly. Thus, the Wilcoxon

Signed Ranks Test showed that the GSR for all the neutral stimuli were significantly

lower in comparison to the aversive stimuli. The results confirm that the

physiological arousal is significantly higher for aversive stimulus as compared to

neutral stimulus when presented at the supraliminal level.

The present results are in line with those of Liberzon, Taylor, Fig, Decker,

Koeppe and Minoshima (2000) and Maren (2001) who also reported a higher

arousal in response to aversive stimuli as compared to neutral. Fear conditioning has

been used as a behavioral paradigm in which organisms learn to predict aversive

events. It is a form of learning in which an aversive stimulus (e.g. an electrical

shock) is associated with a particular neutral context (e.g., a room) or neutral

stimulus (e.g., a tone), resulting in the expression of fear responses to the originally

neutral stimulus or context. This is done by pairing the neutral stimulus with an

aversive stimulus (e.g., a shock, loud noise, or unpleasant odor) such that the neutral

stimulus alone can elicit the state of fear. Fear conditioning has been studied in

numerous species, from snails to humans. In humans, conditioned fear is often

measured with verbal report and galvanic skin response. Changes in rate, breathing,

and muscle responses via electromyography can also be used to measure conditioned

fear (Maren, 2001). Liberzon, Taylor, Fig, Decker, Koeppe and Minoshima (2000)

mapped regional brain activity and peripheral psychophysiological responses,

occurring in response to evocative emotional stimuli. Aversive pictures, relative to

neutral pictures, increased cerebral activity in bilateral amygdala,

thalamic/hypothalamic area, midbrain, and left lateral prefrontal cortex, along with

greater skin conductance responses (SCR

aversive stimuli was a neutral stimuli which had been made aversive by fear

conditioning and a significantly higher GSR score

stimuli.

Assessment of GSR in response to Aversive Stimuli

The investigator had presented three aversive stimuli, where two were presented at

the subliminal and one at supraliminal level.

Table 5.11. Mean and SD o

Aversive stimuli Mean

Sub(S3) 182.07

Supra(S6) 179.46

Sub(S9) 186.89

The mean GSR in response to the

5.11. Surprisingly the aversive stimuli had a higher

subliminally in comparison to the supraliminal presentation

for aversive subliminal words are 182.07 and 186.89 respectively

mean GSR score for supraliminal aversive stimuli is lower i.e. 179.46. These GSR

scores have been shown in Figure 5.5.

Figure5.5. Mean GSR scores in response to aversive stimuli.

174

176

178

180

182

184

186

188

S3

GSR


107

greater skin conductance responses (SCR). In the present investigation also, the


conditioning and a significantly higher GSR score was observed in response to this



the subliminal and one at supraliminal level.

of GSR scores in response to Aversive stimuli

Mean SD Mean Rank

182.07 59.96 1.73

179.46 41.71 2.30

186.89 50.21 1.96

The mean GSR in response to the aversive stimuli have been presented in Table

Surprisingly the aversive stimuli had a higher mean GSR score when presented

subliminally in comparison to the supraliminal presentation. The mean GSR scores

for aversive subliminal words are 182.07 and 186.89 respectively. However, the

supraliminal aversive stimuli is lower i.e. 179.46. These GSR

scores have been shown in Figure 5.5.

Mean GSR scores in response to aversive stimuli.

S6 S9

Stimulus Number


In the present investigation also, the


was observed in response to this


scores in response to Aversive stimuli.

Mean Rank

1.73

2.30

1.96

aversive stimuli have been presented in Table

when presented

The mean GSR scores

However, the

supraliminal aversive stimuli is lower i.e. 179.46. These GSR

Supra

Sub


108

From the Figure 5.5 it can be seen that the aversive subliminal stimuli had a higher

GSR score as compared to aversive supraliminal stimulus.

In order to determine whether the difference among GSR scores in response to the

aversive stimuli was statistically significance, Friedman test was applied. The

analysis revealed that there was a statistically non-significance difference among the

mean GSR in response to the three aversive stimuli. (χ2 (2) = 50 4.70, p = .095)

These results show that the aversive stimuli elicit strong physiological arousal even

when presented at the subliminal level. These results receive support from a study

by Lazarus and McCleary (1951) who found that the GSR responses were greater in

magnitude following the presentation of syllables previously paired with shock,

independent of whether or not these syllables hat been correctly identified. Corteen

and Wood (1972) asked people to report a stream of prose presented to one ear while

words of which they remained unaware were presented to the other ear. It was found

that words presented to the unattended-to ear which had previously been associated

with electric shock, produced an emotional response i.e. a change in skin resistance

due to sweating, without interfering with the attention task of 'shadowing' prose on

the other ear. Further support is evident from a recent pioneer study by Flo, Steine

, Blågstad , Grønli , Pallesen and Portas (2011) who used an aversive imaging

conditioning protocol successfully during sleep in order to identify measurable

physiological responses linked to the human experience of distress in a non-

communicative state. Since sleep is a state of sensory-motor detachment in which

subjects cannot report how they feel or what they experience, it can be compared to

non communicative states such as subliminal perception. Changes in frontal alpha

asymmetry (FAA) were analyzed in 16 volunteers before and after administration of

distressful aversive stimuli during sleep. Transient physical or emotional distress

was achieved by presentation of conditioned (to electroshocks or affective images)

or directly-applied aversive stimuli (electroshocks). Power spectrum data were

assessed from frontal electroencephalographic (EEG) leads (F3/F4) and GSR and

heart rate were also simultaneously monitored. Aversive stimulation of diverse

nature, compared to neutral valence stimuli, produced measurable changes in FAA


109

(left>right) and in GSR evoked responses in both stage 2 (S2) and rapid eye

movement (REM) sleep suggesting implicit processing of experiences with negative

valence. Thus, in the present study also, aversive stimuli were processed even when

presented at a subliminal level, thereby leading to physiological arousal comparable

to supraliminally presented aversive stimuli.


The mean GSR scores in response to the seven neutral stimuli have been presented

in Table 5.12.

Table 5.12. Mean and SD of GSR scores in response to Neutral Stimuli.

Neutral Mean SD Mean Rank

Supra(S1) 141.78 24.47 3.50

Supra(S2) 146.23 33.93 4.00

Supra(S4) 142.10 38.92 3.96

Sub(S5) 149.85 44.74 4.48

Sub(S7) 146.60 41.35 3.98

Supra(S8) 150.89 50.68 3.93

Supra(S10) 157.10 48.66 4.14

From the table it can be seen that the neutral subliminal stimuli had a GSR score of

149.85 and 146.6. However, the minimum score for the supraliminal neutral stimuli

was 141.78 while the maximum was 157.10. These means have graphically depicted

in Figure 5.6.

Figure5.6. Mean GSR scores in response to Neutral Stimuli

From Figure 5.6 it can be seen that the GSR for all the neutral words was more than

the baseline score (all scores are above 130, which

negative valance in the deviation scores). Further GSR increased successively with

nearly presentation except S4

In order to determine whether the difference among the mean GSR scores in

response to the neutral stimuli was sta

applied. The analysis revealed that there was a statistically non

difference among the mean GSR scores for the neutral stimuli. (

.791)

These results are rather surprising as the inv

for neutral stimuli when presented in subliminal form. A number of researches have

consistently demonstrated that subliminal stimuli are capable to inducing

physiological arousal (Dixon & Henley, 1991; Swingle, 1991,

Discriminatory electrodermal responses (EDR’s) have been reported in response to

stimuli presented at speed too rapid for conscious recognition (Lazarus and

McCleary, 1951). The subliminal stimuli generally evoke a lower physiological

arousal as the subject is unaware of the presentation.

130

135

140

145

150

155

160

S1 S2

GSR


110

scores in response to Neutral Stimuli.


the baseline score (all scores are above 130, which were added to remove the


4 and S7.


response to the neutral stimuli was statistically significant, Friedman test was

The analysis revealed that there was a statistically non-significance

among the mean GSR scores for the neutral stimuli. (χ2 (6) = 3.13,

These results are rather surprising as the investigator had expected a lower arousal



physiological arousal (Dixon & Henley, 1991; Swingle, 1991, Taylor, 1997).




l as the subject is unaware of the presentation.

S4 S5 S7 S8 S10

Stimulus Number



added to remove the



tistically significant, Friedman test was

significance

(6) = 3.13, p =

estigator had expected a lower arousal



Taylor, 1997).




Supra

Sub


111

However, in the present investigation, the subject perceived a flash of light when the

stimulus was presented at the subliminal level but since the presentation period was

very brief and contrast between stimulus and background color was very low, the

word could not be recognized. Thus, it is probable that the inability to recognize the

word might have contributed to the increase in arousal to the subliminally presented

neutral stimuli.

Considered together, the results of Phase II, which was conducted with the objective

to study the quantitative difference in physiological arousal in response to neutral

and aversive stimuli presented at subliminal and supraliminal levels, confirms the

fact that the GSR was significantly higher for subliminal aversive stimuli as

compared to subliminal neutral stimuli. The same results were observed on

supraliminal presentation of aversive stimuli as compared to neutral stimulus i.e. the

supraliminal aversive stimuli elicited a significantly higher arousal response in

comparison to the neutral supraliminal stimulus. Thus, the present results confirm

the second hypothesis which predicted that physiological arousal responses to

emotion ladden stimuli (both supraliminal and subliminal) would be would be more

intense as compared to neutral stimuli.

However, no significant difference was observed in the physiological arousal

response between the supraliminal and subliminal aversive stimuli. Similarly,

comparison of neutral stimuli did not elicit a significant difference in the

physiological arousal for the supraliminal and subliminal stimuli. Similar results had

been observed in Phase I where the variation in skin conductance (GSR) in response

to subliminal (subjective threshold) neutral stimuli was found to be comparable to

that of supraliminal stimuli, especially when pooled across a group of subjects.

Thus, on the basis of the present results, it can be concluded that conditioned

aversive stimuli elicit a significantly stronger physiological arousal response in

comparison to neutral stimuli irrespective of nature of presentation. Further, as per

the present experimental manipulations, the physiological response to the subliminal

stimuli is similar to the supraliminal stimuli, may be because the stimuli were

presented at regular intervals and the subject perceived a flash of light on the screen

during the subliminal presentation where the stimulus could not be deciphered. The

inability to recognize the stimulus might have contributed to the increased arousal.

Since no difference was observed in the arousal response to aversive stimuli when


112

presented at subliminal or supraliminal level it appears that the aversive stimulus

was so potent that it elicited an equally strong physiological response even when

presented at the subliminal level.

Phase III

The third objective of the present research was to study the effectiveness of

subliminal stimuli in reducing the probability of use of countermeasures. Two types

of countermeasures (Physical & Mental) were used for the current study. Subjects

were trained for using countermeasures i.e. giving fake response in order to increase

the arousal level. For physical countermeasure, toes to the floor and for mental

countermeasure, counting backward by 7 were used and subjects were asked to use

the countermeasure against the neutral stimuli. As in Phase I, here again, each

subject was shown ten words (3 aversive & 7 neutral) and physiological arousal

GSR was recorded during the presentation period while the countermeasure was

used by subjects in response to neutral stimuli. Baseline and resistance score of

subjects in response to each of the ten stimuli (neutral/aversive;

subliminal/supraliminal) were calculated from the graphical recoding, and then

deviation from the baseline score was computed. These scores were converted into

resistance scores which were further statistically converted as in Phase I.

Initially the GSR scores of the subjects, where physical countermeasures had been

executed against the neutral stimuli, have been considered.

Physical Countermeasures

The statistically converted GSR scores, in response to the ten stimuli where physical

countermeasures were used, have been presented in Table 5.13.


113

Table 5.13. GSR score in response to stimuli, where physical countermeasures

were used on presentation of neutral stimuli.

Stimulus Number

Sr.No. S1

sup(N) S2

sup(N)

S3

sub-A

S4

sup(N)

S5

sub-N

S6

sup-A

S7 sub-N

S8 sup-N

S9

sub-A

S10

sup-N

1 90 72 90 37 32 72 38 54 67 37

2 127 141 158 135 78 82 76 86 97 105

3 131 131 131 130 87 132 89 127 130 128

4 132 133 134 133 82 135 79 136 135 140

5 113 148 113 113 58 113 64 130 116 59

6 125 221 221 227 60 81 61 93 93 65

7 141 287 304 242 102 201 140 164 214 164

8 134 147 140 140 98 140 107 121 138 112

9 120 120 145 145 94 145 91 145 157 115

10 125 131 128 123 99 112 102 121 113 108

11 121 130 130 112 51 78 50 78 94 53

Mean 123.5 151 154 139.7 76.4 117.3 81.5 114 123 98.7

GSR scores in response to the 4 subliminal (2 aversive and 2 neutral) and 6

supraliminal (1 aversive & 5 neutral) stimuli are shows in the Table 5.13. Perusal of

the individual GSR scores showed that the GSR against first supraliminal neutral

stimulus (S1) was lower (except for sub. no, 1) as compare to second supraliminal

neutral stimulus (S2). On the next subliminal aversive stimulus (S3), GSR of all

subjects (except for sub. no. 1, 2, 7 & 9) decreased as compare to second

supraliminal neutral stimulus. Next stimulus in the presentation was a neutral

supraliminal (S4) stimulus and GSR score on this stimulus (supra) was lower than

the previous subliminal aversive stimulus (except for sub. no 6). The reason could be

attributed to the fact that the subjects used the countermeasure against the neutral

stimuli. The next neutral stimulus (S5) was subliminal (N) and GSR score for this

stimulus was also lower as compared to previous supraliminal neutral stimulus (S4)

for all the subjects, indicating that subjects could not use the physical

countermeasure against the subliminal neutral stimulus. Next stimulus (S6) was an

aversive supraliminal stimulus and GSR score for this stimulus was higher as

compared to previous subliminal neutral stimuli (S5). The next stimulus (S7) was

again a neutral subliminal stimulus and GSR score for this stimulus was also lower

as compared to previous supraliminal stimulus (S6) for all the subjects. The eighth

stimulus was a neutral supraliminal stimulus and GSR score for this stimulus was

higher as compared to previous subliminal neutral stimulus (S7). The ninth stimulus

was an aversive subliminal stimulus (S9) and the GSR scores was (except for sub.

no. 4, 5) higher as compare to previous supraliminal neutral stimulus (S8)

stimulus (S10) was a neutral supraliminal stimulus and surprisingly GSR score for

this stimulus was lower (except for sub. no. 2, 4) as compared to previous subliminal

aversive stimulus (S9).

Thus, the individual GSR scores show that the GSR score

supraliminal neutral stimuli are nearly similar to or more than those in response to

the aversive stimuli (either supraliminal or subliminal) while the GSR scores in

response to the two subliminal neutral stimuli were found to be consi

for all the subjects. This fact can be seen from the means also where the GSR

scores in response to the two subliminal stimuli were 76.4 and 81.5 while that in

response to the neutral supraliminal or aversive ( subliminal or supraliminal)

varied from 98.7 to 154. Thus it appears that countermeasures were executed in

response to the supraliminal neutral stimuli but could not be given in response to the

subliminal neutral stimuli.

Figure 5.7. Mean GSR

countermeasures were used on presentation of neutral stimuli.

0

20

40

60

80

100

120

140

160

180

S1 S2 S3

GSR


114



no. 4, 5) higher as compare to previous supraliminal neutral stimulus (S8)



Thus, the individual GSR scores show that the GSR scores in response to the



response to the two subliminal neutral stimuli were found to be consistently lower



response to the neutral supraliminal or aversive ( subliminal or supraliminal)



Mean GSR score in response to stimuli, where physical

countermeasures were used on presentation of neutral stimuli.

S4 S5 S6 S7 S8 S9

Stimulus Number




no. 4, 5) higher as compare to previous supraliminal neutral stimulus (S8). Last



s in response to the



stently lower



response to the neutral supraliminal or aversive ( subliminal or supraliminal) stimuli



in response to stimuli, where physical

S10

Sub-A

Sub-N

Sup-N

Sup-A


115

From Figure 5.7 also, it is evident that arousal was lower in response to neutral

subliminal stimuli as compared to neutral supraliminal or aversive stimulus. It can

be conclude that subjects could not use physical countermeasure against subliminal

neutral stimuli.



data was statistically analyzed in four separate ways in order to study the effect of

subliminal/supraliminal presentation of the probability of use of physical

countermeasure.


The GSR scores in response to the subliminal stimuli (neutral and aversive) were

compared in order to ascertain whether the subliminal stimuli could elicit deferential

physiological arousal (higher GSR in response to aversive stimuli) and whether this

physiological response could be consciously manipulated (use of countermeasures

against the neutral stimuli). The GSR scores in response to the four subliminal

stimuli have been presented in Table 5.14.

Table 5.14. Mean and SD of GSR scores in response to subliminal stimuli when

physical countermeasures were used for neutral stimuli.

Subliminal Mean SD Mean Rank

A(S3) 154.00 59.36 3.73

N(S5) 76.45 23.04 1.36

N(S7) 81.54 28.78 1.64

A(S9) 123.09 39.44 3.27

The mean GSR scores in response to subliminal stimuli have been presented in

Table 5.14. The neutral stimuli had lower mean GSR scores as compared to the

aversive stimuli. All stimuli were presented at subliminal level. The mean value for

first aversive stimulus (S3) was 154 while that for the second aversive stimulus (S9)

was 123.09. Neutral words presented at subliminal level, showed lower mean score

as compared to the aversive stimuli. The mean GSR score of first neutral stimulus

(S5) was 76.45 and second ne

These mean values have been depicted in Figure 5.8.

Figure5.8. Mean GSR scores in response to subliminal stimuli when physical

countermeasures were used for neutral stimuli.

Figure 5.8 clearly indicates that subjects could not use countermeasures against

neutral stimuli. Since two of the stimuli were aversive, subjects GSR w

response to these stimuli.

Thus, On the basis of mean scores, it appears that the subjects could not use the

countermeasure against subliminal neutral stimuli.

In order to determine whether the differences among the GSR scores in response

the subliminal stimuli was statistically significant, Friedman Test was applied.

Analysis revealed that there was a statistically significant

among the subliminal stimuli (

The difference between the GS

applying Wilcoxon Test.

0

20

40

60

80

100

120

140

160

180

S3

GSR


116


(S5) was 76.45 and second neutral stimulu (S7) had a mean GSR score of 81.54.

These mean values have been depicted in Figure 5.8.

scores in response to subliminal stimuli when physical


clearly indicates that subjects could not use countermeasures against

neutral stimuli. Since two of the stimuli were aversive, subjects GSR was higher in


countermeasure against subliminal neutral stimuli.

In order to determine whether the differences among the GSR scores in response


Analysis revealed that there was a statistically significant difference in mean GSR

among the subliminal stimuli ( χ2 (3) = 27.32, p = .000).

The difference between the GSR scores of the various groups was analyzed by

S5 S7 S9

Stimulus Number



utral stimulu (S7) had a mean GSR score of 81.54.

scores in response to subliminal stimuli when physical

clearly indicates that subjects could not use countermeasures against

as higher in


In order to determine whether the differences among the GSR scores in response to


mean GSR

R scores of the various groups was analyzed by

Aversive

Neutral


117

Table 5.15. Significance of difference between the GSR scores in response to

subliminal aversive and neutral stimuli.

Comparisons

between AS3-NS5 AS3-NS7 AS9-NS5 AS9-NS7 NS5-NS7 AS3-AS9

Z Score -2.934a -2.934

a -2.936

b -2.934

b -1.428

b -2.001

a

p .003 .003 .003 .003 .153 .045

From Table 5.15, it can be seen that all the pairs of neutral and aversive stimuli were

significantly different from each other. The two aversive stimuli were significantly

different from the neutral stimuli. Although the GSR in response to the two aversive

stimuli was statistically significant (GSR was higher for S3 as compared to S9), no

significance difference was observed between the GSR scores in response to the two

neutral stimuli.

These results are similar to those observed in Phase I, where a significantly higher

GSR score was observed in response to the aversive subliminal stimuli in

comparison to the neutral subliminal stimuli.

Assessment of GSR in response supraliminal stimuli

The GSR in responses to the supraliminal stimuli were compared in order to

ascertain whether use of countermeasures against the neutral stimuli could increase

the physiological arousal so that the response to the neutral and aversive stimuli

could not be distinguished. The experimenter had presented six stimuli at

supraliminal level where 5 were neutral and one was aversive. The mean GSR

scores for aversive and neutral stimuli, presented at supraliminal level have been

shown in Table 5.16.

Table 5.16. Mean and SD of GSR scores in response to supraliminal stimuli

when physical countermeasures have been used for neutral stimuli.

Supraliminal Mean SD Mean Rank

N(S1) 123.54 13.46 3.55

N(S2) 151.00 56.82 5.00

N(S4) 139.72 55.30 3.95

A(S6) 117.36 38.76 3.50

N(S8) 114.09 32.54 3.09

N(S10) 98.72 40.00 1.91

The mean GSR scores in response to aversive and neutral stimuli (where

countermeasures were used) shows that the GSR in response to the neutral words

was higher than or nearly equal to that in response to the aversive word. The mean

GSR score for the aversive stimulus is 117 while the highest mean score in response

to neutral stimuli is 151.0 while the lowest is 98.73. These GSR scores have been

depicted in Figure 5.9.

Figure5.9. Mean GSR scores in response to supraliminal stimuli when physical

countermeasures have been used for neutral stimuli.

Figure 5.9 clearly indicates that subjects used countermeasure against

thereby leading to elevation of the physiological arousal in response to the neutral

stimuli.


the six supraliminal stimuli was statistically significance, Fri

applied. Analysis revealed that there was a statistically significance

mean GSR among the supraliminal stimuli. (

0

20

40

60

80

100

120

140

160

S1 S2

GSR


118

mean GSR scores in response to aversive and neutral stimuli (where


nearly equal to that in response to the aversive word. The mean


while the lowest is 98.73. These GSR scores have been

Mean GSR scores in response to supraliminal stimuli when physical

countermeasures have been used for neutral stimuli.

9 clearly indicates that subjects used countermeasure against neutral stimuli



the six supraliminal stimuli was statistically significance, Friedman Test was

Analysis revealed that there was a statistically significance difference in

mean GSR among the supraliminal stimuli. (χ2 (5) = 16.91, P = .005)

S4 S6 S8 S10

Stimulus Number


mean GSR scores in response to aversive and neutral stimuli (where


nearly equal to that in response to the aversive word. The mean


while the lowest is 98.73. These GSR scores have been

Mean GSR scores in response to supraliminal stimuli when physical

neutral stimuli



edman Test was

difference in

S10

Neutral

Aversive


119

The differences between the GSR scores in response to the aversive stimulus in

comparison to the six neutral stimuli were analyzed by applying Wilcoxon Test

(non-parametric).

Table 5.17. Significance of difference between the mean GSR scores of the

supraliminal aversive and neutral stimuli.

Comparison

between AS6-NS1 AS6-NS2 A S6-NS4 A S6-NS8 A S6-NS10

Z score -.561 -1.988 -1.40 -.533 -2.224

p .575 .047 .161 .594 .026

Table 5.17 shows that GSR was significantly lower/higher against neutral stimuli S2

and S10 when compared to the GSR against the aversive stimuli, while that against

the remaining neutral stimuli i.e. S1, S4, S8 was not significant. These results indicate

that countermeasures were used in response to all neutral stimuli except the last one

i.e. S10.

These results are at variance with those observed in Phase II, where the GSR in

response to the supraliminally presented aversive stimuli was found to be

significantly higher that the GSR in response to the neutral stimuli. Thus, it appears

that the subjects used physical countermeasures against the neutral and therefore the

physiological arousal was found to be significantly higher or equal to that in

response to the aversive stimuli.


The GSR in response to the aversive stimuli were compared in order to ascertain

whether there was any difference in the physiological response to

subliminal/supraliminal presentation of an emotionally toned stimuli.

Table-5.18 Mean and SD

physical countermeasures were used for aversive stimuli.

Aversive Mean

Sub(S3) 154.00

Supra(S6) 117.36

Sub(S9) 123.09

The mean and SD of the GSR

Table 5.18. The mean scores against both subliminal aversive stimuli (154 &

123.09) are higher as compared to the supraliminal aversive stimuli (117.36). These

mean GSR score have been depicted in Figure 5.10.

Figure5.10. Mean of GSR scores in response to aversive stimuli when physical

countermeasures have been used for aversive stimuli.

From the figure it is evident that subjects arousal was higher for the two

stimuli in comparison to the supraliminal stimuli.


the three aversive stimuli, was statistically significant, Friedman’s test was applied.

Analysis revealed that there was no statistically significant difference

mean GSR scores in response to aversive stimuli. (

0

20

40

60

80

100

120

140

160

180

S3

GSR


120

of GSR scores in response to aversive stimuli when

physical countermeasures were used for aversive stimuli.

Mean SD Mean Rank

154.00 59.36 2.41

117.36 38.76 1.64

123.09 39.44 1.95

The mean and SD of the GSR scores, in response to aversive stimuli are presented in



mean GSR score have been depicted in Figure 5.10.

of GSR scores in response to aversive stimuli when physical

countermeasures have been used for aversive stimuli.

it is evident that subjects arousal was higher for the two subliminal

stimuli in comparison to the supraliminal stimuli.



here was no statistically significant difference among the

mean GSR scores in response to aversive stimuli. ( χ2 (2) = 3.65, p = .165). These

S6 S9

Stimulus Number


aversive stimuli when

Mean Rank

2.41

1.64

1.95

response to aversive stimuli are presented in



of GSR scores in response to aversive stimuli when physical

subliminal



among the

= .165). These

Sub

Supra


121

results are similar to those observed in Phase II, where no significant difference was

observed in response to the aversive stimuli presented at either supraliminal or

subliminal level. Thus, it appears that the aversive stimuli were perceived by the

subject, even when presented in subliminal form, thereby leading to elevation of

physiological arousal to a level comparable with that in response to the supraliminal

aversive stimuli.


The GSR score is responses to the seven neutral stimuli were compared to in order

to ascertain whether the physical countermeasures had been executed irrespective of

the nature of presentation i.e. subliminal/supraliminal.

Table5.19. Mean and SD of GSR scores in response to neutral stimuli when

physical countermeasures have been used for neutral stimuli.

Neutral

Stimuli Mean SD Mean Rank

Supra(S1) 123.54 13.46 5.05

Supra(S2) 151.00 56.82 6.32

Supra(S4) 139.72 55.30 5.27

Sub(S5) 76.45 23.04 1.36

Sub(S7) 81.54 28.78 1.91

Supra(S8) 114.09 32.54 4.55

Supra(S10) 98.72 40.00 3.55

The mean GSR and SD have been presented in Table 5.19. The highest mean GSR

score in response to the neutral supraliminal stimuli was 151.0 while the lowest was

98.72 while that in response to the two neutral subliminal stimuli were lower (76.45

and 81.54). Thus, it appears that the subliminal stimuli elicited a weaker

physiological arousal as the subjects could not execute the countermeasure in the

absence of conscious awareness, while countermeasures were definitely executed in

response to some of the supraliminal neutral stimuli. Mean GSR score in response to

the neutral stimuli have been depicted in Figure 5.11.

Figure5.11. Mean GSR scores in response to neutral stimuli when physical


From Figure 5.11 it is evident that the GSR in response to the subliminal stimuli

were lower than in response to supraliminal stimuli.


the seven neutral stimuli was statistically significance, Friedman test was applied.

Analysis revealed that there was a statistically significant difference among the

mean GSR scores in response to the seven neutral stimuli (

The difference between the GSR scores in response to subliminal stimuli were

compared with those for the five supraliminal stimuli by applying Wilcoxon test.

Table 5.20. Significance of difference

supraliminal neutral stimuli wh

neutral stimuli.

Subliminal S1

S5 Z scores

-2.936

Significance .003

S7 Z scores

-2.934

Significance .003

0

20

40

60

80

100

120

140

160

S1 S2

GSR


122

Mean GSR scores in response to neutral stimuli when physical

used for neutral stimuli.

11 it is evident that the GSR in response to the subliminal stimuli

were lower than in response to supraliminal stimuli.


tral stimuli was statistically significance, Friedman test was applied.


mean GSR scores in response to the seven neutral stimuli (χ2 (6) = 47.47, p= .000).

between the GSR scores in response to subliminal stimuli were


of difference between the GSR score of subliminal and

supraliminal neutral stimuli when physical countermeasures had been used for

Supraliminal

S1 S2 S4 S8

2.936 -2.934 -2.936 -2.936

.003 .003 .003 .003

2.934 -2.936 -2.847 -2.934

.003 .003 .004 .003

S4 S5 S7 S8

Stimulus Number


Mean GSR scores in response to neutral stimuli when physical

11 it is evident that the GSR in response to the subliminal stimuli


tral stimuli was statistically significance, Friedman test was applied.


= .000).

between the GSR scores in response to subliminal stimuli were


R score of subliminal and

en physical countermeasures had been used for

S10

-2.936

.003

-2.447

.014

S10

Sup

Sub


123

The Wilcoxon analysis showed that mean GSR scores in response to the subliminal

stimuli were significantly lower than the GSR scores in response to the supraliminal

stimuli while the difference between the GSR scores of the two subliminal neutral

stimuli (S5 and S7) was non-significant(Z= -1.428, p=.156). Comparison of these

results with those of Phase II shows that no significant difference was observed in

the physiological arousal in response to the neutral stimuli when presented at either

subliminal or supraliminal level.

Since, the GSR scores of the subjects who were instructed to use countermeasure on

presentation of the neutral stimuli, were significantly higher for supraliminal neutral

stimuli in response to the subliminal stimuli it appears that countermeasures could

be executed in response to the neutral supraliminal stimuli but not to the subliminal

neutral stimuli which did not result in conscious awareness.

Considered together, the results of this section, where the objective was to study the

effectiveness of subliminal stimuli in reducing the probability of use of physical

countermeasures, indicate that results obtained on assessment of GSR for subliminal

stimuli(aversive and neutral) and for aversive stimuli (supraliminal and subliminal)

are in congruence to those observed for Phase II. These results indicate that aversive

stimuli elicit a strong physiological arousal response even when presented

subliminally. Assessment of GSR in response to supraliminal (aversive and neutral)

and neutral stimuli (supraliminal and subliminal) presented a different picture in

comparison to Phase II. Here, the physiological arousal response to the supraliminal

neutral stimuli was found to be equal to/or significantly higher than that to the

supraliminal aversive stimuli, implicating the use of counter measures against the

supraliminal neutral stimuli, thereby resulting in an elevation in the physiological

arousal such that it could not be differentiated from that in response to the aversive

stimuli. Comparison of the neutral supraliminal and subliminal stimuli showed that

the physiological arousal was significantly lower for the subliminal stimuli in

comparison to the response to the supraliminal stimuli while the difference between

the two subliminal neutral stimuli was non-significant. These results clearly indicate

that the subjects could not execute the countermeasure in response to the subliminal

neutral stimuli. Thus, the present results confirm the third hypothesis which


124

predicted that use of physical countermeasures would be more for supraliminal

stimuli as compared to subliminal stimuli.

Some laboratory studies (by office of Technology Assessment, 1983; Raskin, 1986)

have shown that physical countermeasures such as bitting one’s tongue and

pressing the toes to the floor can be effectively utilized by some people in order to

defeat the lie detection procedure. Honts and his colleagues suggested that training

subjects in physical countermeasures or in a combination of physical and mental

countermeasures substantially decreased the likelihood of detection of deceptive

subjects by the polygraph (Honts, 1986; Honts, Raskin & Kircher, 1996; Honts,

Hodes & Raskin, 1985; Honts & Kircher, 1987, 1994; Raskin and Kircher, 1990

).Honts et al. (1987, 1994, & 1996) found that the rate of mistakes made by CQT

and GKT polygraphists testing examinees practicing countermeasures ranged

between 50 and 70%. Mistakes led to false negative outcomes, but not false positive.

There is evidence that the effect of countermeasure can be assessed particularly

through the electrodermal channel-EDR (Elaad and Ben Shakhar, 1991; Ben-

Shakhar and Dolev, 1996).

Research in the area of subliminal perception has demonstrated that stimuli

presented below the subjective subliminal but above the objective subliminal

threshold elicits a physiological arousal response even though it does not result in

conscious awareness (Borgeat et al.,1985; Borgeat & Goulet ,1983; Dixon

,1983;Dixon & Henley, 1991; Swingle, 1991;Taylor, 1994). Significant differences

in EEG and ECG for subliminal emotional and neutral words have been reported by

Emrich and Heinemann (1966). Masling et al. (1991) used an arousing experimental

and a neutral control message reported that subjects exposed to the short duration

arousing message showed a significant increase in EDR when compared to controls.

Borgeat and Goulet (1983) showed a significant effect of the activation subliminal

suggestions during and following a stressing task indicating effects of consciously

unrecognized perceptions on psychophysiological responses.

Kemp-Wheeler and Hill (1987) found that manifest anxiety and some features of

anxiety having somatic referents can be induced by subliminal experience of mild

stress. Kotze and Moller (1990) presented emotional and neutral words subliminally

while recording the GSR and observed a significant increase in GSR response for

emotional but not for neutral words. These researches consistently demonstrate that


125

physiological arousal response to emotional laden stimuli is stronger in comparison

to neutral stimuli.

In the present investigation also, a stronger arousal response was observed in

response to the subliminal aversive stimuli in comparison to the neutral subliminal

stimuli. Since the subliminal neutral stimuli did not result in conscious awareness

the physical countermeasure could not be executed in response to its presentation

and as a consequence the difference in physiological arousal was significantly lower

for the subliminal stimuli in comparison to the response to the supraliminal stimuli

(countermeasure was given in response to consciously perceived neutral stimuli).

The physiological arousal response to the supraliminal neutral stimuli was found to

be equal to/or significantly higher than that to the supraliminal aversive stimuli, as

countermeasure was used against the supraliminal neutral leading to the elevation of

the arousal response such that it was equal to /or more than that observed in response

to the aversive stimuli. Thus, the present results show that the physical

countermeasure could not be used for the subliminal stimuli.

Mental Countermeasure

Research has indicated that subjects tend to use mental countermeasures also in

order to escape detection. In the present investigation a group of 11 subjects were

trained to use a mental countermeasure (counting backward by 7) and the same

procedure as for physical countermeasure was repeated. The mean and SD of the

statistically converted GSR scores of the subjects, while executing mental

countermeasures again the neutral stimuli, have been presented in Table 5.21.


126

Table 5.21. GSR score in response to stimuli, where mental countermeasures

have been used on presentation of neutral stimuli.

Stimulus Number

Sr.

No

S1

Sup-N

S2

Sup-N

S3

Sub-A

S4

Sup-N

S5

Sub-N

S6

Sup-A

S7

Sub-N

S8

Sup-N

S9

Sub-A

S10

Sup-N

1 128 130 125 125 120 120 115 115 110 108

2 141 81 72 47 72 47 38 23 15 8

3 123 144 130 130 159 130 123 130 116 103

4 157 150 201 171 171 157 171 157 147 143

5 141 146 201 158 158 195 182 170 208 235

6 135 140 143 140 139 136 139 139 138 138

7 116 263 303 244 192 283 226 226 263 292

8 122 161 185 212 224 236 256 249 249 256

9 135 171 188 182 177 177 171 166 161 156

10 135 164 206 196 196 185 174 196 174 169

11 151 130 90 90 90 53 71 71 45 80

Mean 134.9 152.7 145.5 154.1 154.3 156.2 151.4 149.2 147.8 153.4

From the GSR scores, it can be seen that the GSR score of the subjects at Sr. No. 1,

2, 3 and 11 is below 130 in response to maximum of the stimuli. This indicates that

their physiological arousal was lower than the baseline during the presentation

period. This is difficult to comprehend as the subject has been instructed to use the

mental countermeasures. Perusal of the GSR scores in comparison to the preceding

score in response to the various stimuli shows that the GSR score in response to S1

was found to be slightly higher than the baseline score for subjects at Sr. no. 4, 5, 6,

9, 10, and 11. In response to S2 an increase was seen in sub no. 1, 3,6,8,9 and 10.

Surprisingly the score in response to S3, which was a subliminal aversive stimulus,

was relatively higher than S2 in case of sub. no. 4, 7, 8 and 10. For the remaining

subjects it was slightly higher or lower. The next GSR score in response to S4

(supraliminal neutral stimuli) was higher in comparison to S4 only for one subject

indicating that mental countermeasure could not be executed effectively. S5 was a

subliminal neutral stimuli and the investigator had expected a lower GSR score as

use of countermeasure was not expected in response to a subliminal stimuli.

However, here again the score was eit

stimuli except for subject no. 1,7 and 9. The GSR scores for the next five stimuli

were found to be stable or a progressive decrease was seen ,except for sub. no. 5.

These results are rather surprising as all the s

presentation or nature of stimuli. These means have been plotted in Figure 5.12.

Figure5.12. GSR scores in response to stimuli, where mental


From the figure it is clear that some variation in GSR occurred for the first four

stimuli while it was relatively stable for the next six stimuli. The means GSR scores

indicate that either the subjects found it difficult to perform the task i.e. perceiving

the stimuli and using the mental countermeasure simultaneously or the execution

the mental countermeasure might have exceeded the presentation period thereby

leading to a consistent GSR score. In order to compare the GSR score of the similar

stimuli the means were analyses in four sections.


The GSR scores in response to the subliminal stimuli (neutral and aversive) were

compared in order to ascertain whether the subliminal stimuli could elicit



120

125

130

135

140

145

150

155

160

S1 S2 S3

GSR


127

However, here again the score was either equal to or higher than the preceding



These results are rather surprising as all the stimuli differed in terms of nature of


in response to stimuli, where mental countermeasures




r the subjects found it difficult to perform the task i.e. perceiving

the stimuli and using the mental countermeasure simultaneously or the execution

mental countermeasure might have exceeded the presentation period thereby

GSR score. In order to compare the GSR score of the similar

stimuli the means were analyses in four sections.


in response to the subliminal stimuli (neutral and aversive) were

scertain whether the subliminal stimuli could elicit



S4 S5 S6 S7 S8 S9 S10

Stimulus Number


her equal to or higher than the preceding



timuli differed in terms of nature of


countermeasures



r the subjects found it difficult to perform the task i.e. perceiving

the stimuli and using the mental countermeasure simultaneously or the execution of

mental countermeasure might have exceeded the presentation period thereby

GSR score. In order to compare the GSR score of the similar

in response to the subliminal stimuli (neutral and aversive) were

scertain whether the subliminal stimuli could elicit



Sub-N

Sub-A

Sup-N

Sup-A

against the neutral stimuli). The GSR s


Table 5.22. Mean and SD o

mental countermeasures were used for neutral stimuli.

Subliminal Mean

A(S3) 145.54

N(S5) 154.36

N(S7) 151.45

A(S9) 147.81

The mean GSR score for the first aversive stimulus (S

second aversive stimulus (S

higher mean score as compare to the aversive stimuli. The mean score of first neutral

stimulus (S5) is 154.3 and second neutral stimulus (S

been depicted in Figure 5.13.

Figure 5.13. Mean GSR scores in response to subliminal stimuli when mental

countermeasures used for neutral stimuli.

140

142

144

146

148

150

152

154

156

S3

GSR


128

against the neutral stimuli). The GSR scores in response to the four subliminal


of GSR scores in response to subliminal stimuli


Mean SD Mean Rank

145.54 40.16 2.82

154.36 46.00 2.91

151.45 63.50 2.50

147.81 76.64 1.77

The mean GSR score for the first aversive stimulus (S3) is 145.5 while that for the

second aversive stimulus (S9) is 147.8.The neutral subliminal stimuli showed


) is 154.3 and second neutral stimulus (S7) is 151.4. These means have

been depicted in Figure 5.13.

Mean GSR scores in response to subliminal stimuli when mental

countermeasures used for neutral stimuli.

S5 S7 S9

Stimulus Number


cores in response to the four subliminal

subliminal stimuli when

Mean Rank

2.82

2.91

2.50

1.77

) is 145.5 while that for the

) is 147.8.The neutral subliminal stimuli showed a


) is 151.4. These means have

Mean GSR scores in response to subliminal stimuli when mental

Aversive

Neutral


129

From the Figure 5.13 it appears that the subjects used countermeasure even for the

neutral subliminal stimuli as the GSR scores were higher than those for the aversive

subliminal stimuli.


the subliminal stimuli were statistically significance, Friedman Test was applied

Analysis revealed that the difference was not statistically significance (χ2 (3) =5.51,

P = .138).

Thus, it is evident that the subject’s arousal level was similar to the neutral as well as

the aversive stimuli, when presented at a subliminal level. These results are in

contradiction to those of the present investigation where physical countermeasures

had been used and GSR scores in response to neutral stimuli were found to be lower

in comparison the aversive stimuli indicating that the physical countermeasure had

not been used for the subliminal neutral stimuli. The results of the present section

indicate that either the subjects were able to consciously perceive the subliminal

neutral stimuli and give the mental countermeasure or they could not carry out both

the mental processes (perceiving the stimuli and executing the countermeasure)

simultaneously and therefore gave the countermeasure when the presence of a

stimulus was detected, irrespective of its nature.

Assessment of GSR for supraliminal stimuli

The GSR in response to the supraliminal stimuli were compared in order to ascertain

whether use of countermeasures against the neutral stimuli could increase the

physiological arousal so that the response to the neutral and aversive stimuli could

not be distinguished. The experimenter had presented six stimuli at supraliminal

level where five were neutral and one was aversive. The means GSR scores for the

aversive and neutral stimuli, presented supraliminally, have been presented in Table

5.23.

Table 5.23. Mean and SD

when mental countermeasures used for neutral stimuli.

Supraliminal Mean

N(S1) 134.90

N(S2) 152.72

N(S4) 154.09

A(S6) 156.27

N(S8) 149.27

N(S10) 153.45

The mean GSR score for the aversive stimuli is 156.2 while all the neutral

supraliminal stimuli have a lower mean score. The highest mean score for neutral

stimuli was 154.0 while the lowest was 134.90. The means have been graphically

shown in Figure 5.14.

Figure 5.14 Mean GSR scores in response to supraliminal stimuli when mental


Figure 5.14 shows that the GSR in response to all the

similar except for the first neutral stimuli, which appears to be considerably lower.

120

125

130

135

140

145

150

155

160

S1 S2

GSR


130

Mean and SD of GSR scores in response to supraliminal stimuli

when mental countermeasures used for neutral stimuli.

Mean SD Mean Rank

134.90 12.38 2.64

152.72 43.77 3.95

154.09 56.10 4.32

156.27 70.84 3.68

149.27 65.19 3.41

153.45 82.53 3.00






Figure 5.14 shows that the GSR in response to all the supraliminal stimuli was


S4 S6 S8 S10

Stimulus Number


response to supraliminal stimuli

Mean Rank

2.64

3.95

4.32

3.68

3.41

3.00





supraliminal stimuli was


Aversive

Neutral


131

In order to determine whether the difference among the GSR in response to the six

supraliminal stimuli was statistically significance, Friedman Test was applied.

Analysis revealed that there was no significance difference among the mean GSR

scores in response to the supraliminal stimuli ( χ2 (5) = 6.19, P = .288 ).

These results are similar to those observed with physical countermeasures where a

significantly lower GSR was observed only in response to the last stimuli (neutral)

as compared to the aversive stimuli while no significant difference was observed

between the remaining stimuli. These results indicate that either the subjects were

able to use the countermeasures in response to all the neutral stimuli or no attention

was paid to the stimuli and subject executed the countermeasure irrespective of the

nature of stimuli.

Assessment of GSR in response to aversive stimuli

The GSR in response to the aversive stimuli were compared in order to ascertain

whether there was any difference in the physiological arousal to

subliminal/supraliminal presentation of an emotionally toned stimuli.

Table 5.24. Mean and SD of GSR scores in response to aversive stimuli when


Aversive Mean SD Mean Rank

Sub(S3) 145.54 40.16 2.23

Supra(S6) 156.27 70.84 2.23

Sub(S9) 147.81 76.64 1.55

The mean GSR score and SD in response to the three aversive stimuli have been

presented in Table 5.24. The mean scores for subliminal aversive stimuli were

145.5 and 147.8 respectively while the aversive supraliminal stimulus had mean

value of 156.2. These mean have been depicted in Figure 5.15.

Figure 5.15. Mean GSR scores in response to aversive stimuli when mental


From the Figure 5.15 it can be seen that GSR was higher for the supraliminal stimuli

when compared with subliminal

earlier observed results with physical countermeasure.

The difference among the GSR scores in response to the aversive stimuli was

statistically analyzed. Friedman analysis revealed a non significance d

among the mean GSR scores in response to aversive stimuli (

.175). These results are similar to those obtained with physical countermeasures,

indicating that the classically conditioned aversive stimulus elicited a similar

response irrespective of nature of presentation.

Assessment of GSR in response to neutral stimuli

The GSR score is responses to neutral stimuli were compared to in order to ascertain

whether the mental countermeasures had been executed irrespective of the nat

presentation i.e. subliminal/supraliminal. The mean and SD of the GSR scores are

presented in Table 5.25.

140

142

144

146

148

150

152

154

156

158

S3

GSR


132

Mean GSR scores in response to aversive stimuli when mental


15 it can be seen that GSR was higher for the supraliminal stimuli

when compared with subliminal stimuli (aversive). These results again parallel the

earlier observed results with physical countermeasure.


statistically analyzed. Friedman analysis revealed a non significance d

among the mean GSR scores in response to aversive stimuli ( χ2 (2) = 3.48



onse irrespective of nature of presentation.

Assessment of GSR in response to neutral stimuli


whether the mental countermeasures had been executed irrespective of the nat


S6 S9

Stimulus Number


Mean GSR scores in response to aversive stimuli when mental

15 it can be seen that GSR was higher for the supraliminal stimuli

stimuli (aversive). These results again parallel the


statistically analyzed. Friedman analysis revealed a non significance difference

(2) = 3.48, P =




whether the mental countermeasures had been executed irrespective of the nature of


Sub

Supra

Table 5.25. Mean and SD


Neutral

Stimuli Mean

Supra(S1) 134.90

Supra(S2) 152.72

Supra(S4) 154.10

Sub(S5) 154.36

Sub(S7) 151.45

Supra (S8) 149.27

Supra(S10) 153.45

Table 5.22 shows that the mean GSR scores for the two subliminal stimuli were

154.3 and 151.4 respectively while for the supraliminal stimuli the mean GSR scores

varied from 134.90 to 151.45. These mean scores have been depicted in figure 5.16.

Figure 5.16. Mean GSR scores in response to neutral stimuli when mental

were used for neutral stimuli.

From Figure 5.16 it can be seen that, except

were relatively consistent.

125

130

135

140

145

150

155

160

S1 S2

GSR


133

of GSR scores in response to neutral stimuli when


Std. Deviation Mean Rank

12.38 2.91

43.77 4.55

56.10 5.00

46.00 4.73

63.50 4.00

65.19 3.68

82.53 3.14

shows that the mean GSR scores for the two subliminal stimuli were



Mean GSR scores in response to neutral stimuli when mental

were used for neutral stimuli.

can be seen that, except for the first stimuli, the GSR scores

S4 S5 S7 S8 S10

Stimulus number


f GSR scores in response to neutral stimuli when

Mean Rank

2.91

4.55

5.00

4.73

4.00

3.68

3.14

shows that the mean GSR scores for the two subliminal stimuli were



Mean GSR scores in response to neutral stimuli when mental

GSR scores

Sup

Sub


134


the neutral stimuli were statistically significant, Friedman test was applied. Analysis

revealed that the difference among the means were not statistically significant (χ2 (6)

= 9.46, P = .149).

These results indicate that subjects were executing the countermeasures irrespective

of nature of stimuli since the physiological arousal in response to the neutral

subliminal stimuli (which was below the conscious awareness threshold) was equal

to that in response to the neutral supraliminal stimuli. These results are in

contradiction to those observed with physical countermeasure where the GSR scores

for the subliminal neutral stimuli were found to be significantly lower than those in

response to the supraliminal neutral stimuli.

Considered together the analysis of this section indicates that the GSR

scores for the neutral subliminal stimuli were higher than those for the aversive

subliminal stimuli indicating that either the subjects were able to consciously

perceive the subliminal neutral stimuli and give the mental countermeasure or they

could not carry out both the mental processes (perceiving the stimuli and executing

the countermeasure) simultaneously and therefore gave the countermeasure when

the presence of a stimulus was detected, irrespective of its nature. The GSR scores in

response to the supraliminal stimuli(neutral and aversive ) did not differ significantly

indicating that either the subjects were able to use the countermeasures in response

to all the neutral stimuli or no attention was paid to the stimuli and subject executed

the countermeasure irrespective of the nature of stimuli. Further analysis of neutral

stimuli revealed that the GSR scores in response to the subliminal stimuli were

similar to those in response to the supraliminal neutral stimuli indicating that

subjects were executing the countermeasures irrespective of nature of stimuli. These

results show that the subjects could not use the mental countermeasures as

effectively as physical countermeasures. Thus the present results do not verify the

fourth hypothesis which predicted that use of mental countermeasures would be

more for supraliminal stimuli as compared to subliminal stimuli.

The present results receive support from a series of studies by Honts and his

colleagues who suggest that training subjects in physical countermeasures or in a


135

combination of physical and mental countermeasures can substantially decrease the

likelihood that deceptive subjects will be detected by the polygraph (Honts, 1986;

Honts, Raskin & Kircher, 1994; Honts, Hodes & Raskin, 1985; Honts & Kircher,

1987, 1994; Raskin and Kircher, 1990). These studies suggest that physical

countermeasures are more effective than mental ones and that a combination of

physical and mental countermeasures is probably the most effective. Honts et al

(1996) examined the efficacy of physical (pressing the toes to the floor) and mental

(counting backward by sevens) countermeasures on the concealed knowledge test

(CKT) in a mock crime experiment with 40 subjects. Some knowledgeable subjects

were informed about the nature of the CKT and were trained in the use of a

countermeasure, whereas others remained uninformed. All subjects were offered a

monetary reward if they could produce a truthful outcome. Subjects were tested

using standard field techniques and instrumentation. The physical counter measure

was found to be more effective while the mental countermeasures were less effective

in reducing the accuracy of the CKT. Elaad and Ben-Shakhar (2009) also reported

that physical countermeasures lowered SCR accuracy while SCR was relatively

resistant to mental countermeasures. Studies of mental countermeasures have also

produced inconsistent findings. In an earlier study, Elaad and Ben-Shakhar (1991)

investigated the effects of mental countermeasures on psychophysiological detection

in a guilty knowledge paradigm where two types of mental countermeasures

(specific dissociations from the relevant stimulus and continuous dissociation

throughout the entire test, as well as a control-no countermeasure condition) were

used. Results revealed that the item-specific countermeasures tended to increase

psychophysiological detection, whereas the continuous dissociations tended to

decrease detection efficiencies. Kubis (1962) and Wakamatsu (1987) presented data

suggesting that some mental countermeasures reduce the accuracy of polygraph

tests. Elaad and Ben-Shakhar (1991) present evidence that certain mental

countermeasures have relatively weak effects, findings that are confirmed by Ben-

Shakhar and Dolev (1996).

In the present investigation the subjects were required to give the mental

countermeasure, counting backwards by 7, in response to discrete stimuli presented

for brief time intervals (0.5/.001 sec).It is probable that the subjects might have


136

found it difficult to perform both the mental tasks (perception of stimulus and

execution of mental countermeasure) simultaneously and therefore the

countermeasure was given irrespective of the nature of stimulus. The presence of the

subliminal stimuli could be discerned (as a flash of light) even in the absence

conscious awareness of the stimulus and this might have been sufficient for eliciting

the mental countermeasure. For physical countermeasures there was a clear cut

segregation of the two tasks (perceiving the stimulus and executing the counter

measure) and this might have reduced the load on the mental resources thereby

leading to allocation of more mental resources to the perceptual task.

The present investigation was conducted to investigate quantitative differences in

physiological arousal response to supraliminal vs subliminal (neutral) and neutral vs

aversive (supraliminal/subliminal) stimulation. Further the effectiveness of

subliminal stimuli in reducing the probability of use of countermeasures (physical

and mental) was considered. The investigation was conducted in three phases where

single group repeated measure/multiple group design experiments were conducted.

Results of Phase I revealed that a short exposure interval (0.001 sec) reduces the

probability of conscious processing of discrete stimuli. Further, the variation in skin

conductance (GSR) in response to subliminal (subjective threshold) stimuli is

comparable to that of supraliminal stimuli, especially when pooled across a group of

subject. In Phase II conditioned aversive stimuli was found to elicit a significantly

stronger physiological arousal response in comparison to neutral stimuli irrespective

of nature of presentation. However, the physiological response to the subliminal

stimuli was similar to the supraliminal stimuli for neutral as well as aversive stimuli.

Phase III, where the effectiveness of subliminal stimuli in deterring the execution of

countermeasures was studied, revealed that subliminal stimuli acted as a deterrent to

physical countermeasures but the effect was not observed in case of mental

countermeasures. Thus, the present results verify the second and third hypotheses

while the first and fourth were not supported.


137

Implications

The results of the present study indicate that:

• Aversive stimuli (classically conditioned, i.e. stimuli which are not

inherently aversive but become aversive due to association with a negative

event) result to a strong physiological arousal even when presented in

subliminal form.

• Subliminal stimuli can be used as a deterrent to countermeasures (Physical)

in Lie Detection for investigation by investigation agencies. It can be

incorporated in the GKT paradigm where the options can be presented in

subliminal form or primed by using a lexical decision paradigm.

Limitations of the Study

• The investigator had used a list of discrete words presented in a successive

manner (with an inter stimulus of 9 second). As a consequence the

physiological arousal response to one stimulus was confounded by that to

the preceding/succeeding stimuli. Use of discrete trials, with each stimulus

presented as a independent item (in a message or as multiple choice

questions) could have helped to isolate the physiological response to each

stimulus.

• The subjects in the present investigation were motivated to give the

countermeasures by the instructions of the investigator. Use of a simulated

situation (deliberate lying by subjects or mock crime) could have provide

intrinsic motivation.

• The investigator had assessed the physiological arousal in response to the

discrete stimuli, some of which were presented in subliminal form.

However, the subjects did not report whether they were consciously aware

of the stimulus or not. Recording of the recognition response of the subjects

during the presentation would have helped to clarify the observed

differences in physiological response to subliminal and supraliminal stimuli.


138

• The stimuli used in the present investigation did not elicit a very strong

physiological arousal response and therefore three indices of physiological

arousal i.e. respiration, blood pressure and pulse rate could not be used.

Suggestions for Further Study

• The use of subliminal stimuli as a deterrent to countermeasures should be

investigated in simulated experimental/field studies (with suspected

criminals)

• The effectiveness of others physiological indices i.e. respiration, blood

pressure and pulse rate in comparison to GSR as a measure for detecting,

faking of physiological response to subliminal stimuli should be

investigated.

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