Lexical Decision Task Performance in Blood-Fearful and Spider-Fearful Individuals F. RICHARD FERRARO, KIM CHRISTOPHERSON, AND JASON DOUGLAS University of North Dakota University undergraduates were pre-screened for blood fearfulness (fear of blood, n = 25), spider fearfulness (fear of spiders, n = 30), or non-fearfulness (n = 23) and presented with blood, spider, neutral, positive, and pseudoword (pronouncable nonword, like flirp) stimuli in a lexical decision task (LDT). Use of the LDT in phobic individu- als may provide insight about how these individuals process, store, and ultimately use information and, in turn, how processing this information affects their day-to-day activities. Words were responded to faster than pseudowords. No group main or interaction effects emerged, and all groups responded faster and more accurately to spider words then blood words and neutral words. Results suggest that the single- word lexical decision task may not be sensitive in detecting lexical processing biases toward threat in these groups. Results also suggest that paradigms that are based on high- level, semantic-conceptualinformation processing (like lexical decision) are not sensitive enough to detect group differences in blood and spider phobias. Any array of percep- tual and conceptual tasks taken together may be needed to detect these differences. S everal studies have investigated the impact that specific phobias (e.g., fear of blood, fear of spiders) have on how individuals process information (Kindt & Brosschot, 1998; Kindt, Brosschot, & Borten, 1999; Rusted & Dighton, 1991; Watts & Coyle, 1992; Watts & Dagleish, 1991). In general, the type of material presented (for example, blood-related, spider-related) has a differential impact on how individuals with a phobia respond. Individuals with a phobia respond to threatening material in a different manner than individuals without a phobia (see Williams et al., 1997, for a comprehensive review). Usually these differences are in the direction of phobic indi- viduals allocating substantial cognitive resources to the detection and processing of threat. The present study intends to investigate how individuals with specific phobias (spiders, blood) process information that is related to their specific phobia. How these individuals process this information may lead to better models of how various phobias affect information processing, comprehension, and understanding of everyday life. To date, most studies investigating information processing (psychological approach to identify what happens during the stages of processing information including atten- tion, short-term memory, perception, long-term memory) among individuals with spe- Current Psychology: Developmental ~ Learning Personality Social Summer 2006, Vol. 25, No. 2, pp. 132-143.
Transcript
Lexical Decision Task Performance in Blood-Fearful and Spider-Fearful Individuals
F. RICHARD FERRARO, KIM CHRISTOPHERSON,
AND JASON D O U G L A S Universi ty o f Nor t h Dako ta
University undergraduates were pre-screened for blood fearfulness (fear of blood, n = 25), spider fearfulness (fear of spiders, n = 30), or non-fearfulness (n = 23) and presented with blood, spider, neutral, positive, and pseudoword (pronouncable nonword, like flirp) stimuli in a lexical decision task (LDT). Use of the LDT in phobic individu- als may provide insight about how these individuals process, store, and ultimately use information and, in turn, how processing this information affects their day-to-day activities. Words were responded to faster than pseudowords. No group main or interaction effects emerged, and all groups responded faster and more accurately to spider words then blood words and neutral words. Results suggest that the single- word lexical decision task may not be sensitive in detecting lexical processing biases toward threat in these groups. Results also suggest that paradigms that are based on high- level, semantic-conceptual information processing (like lexical decision) are not sensitive enough to detect group differences in blood and spider phobias. Any array of percep- tual and conceptual tasks taken together may be needed to detect these differences.
S everal studies have investigated the impact that specific phobias (e.g., fear o f blood, fear of spiders) have on how individuals process information (Kindt &
Brosschot, 1998; Kindt, Brosschot, & Borten, 1999; Rusted & Dighton, 1991; Watts & Coyle, 1992; Watts & Dagleish, 1991). In general, the type of material presented (for example, blood-related, spider-related) has a differential impact on how individuals with a phobia respond. Individuals with a phobia respond to threatening material in a different manner than individuals without a phobia (see Williams et al., 1997, for a comprehensive review). Usually these differences are in the direction of phobic indi- viduals allocating substantial cognitive resources to the detection and processing of threat. The present study intends to investigate how individuals with specific phobias (spiders, blood) process information that is related to their specific phobia. How these individuals process this information may lead to better models of how various phobias affect information processing, comprehension, and understanding of everyday life.
To date, most studies investigating information processing (psychological approach to identify what happens during the stages o f processing information including atten- tion, short-term memory, perception, long-term memory) among individuals with spe-
Current Psychology: Developmental ~ Learning �9 Personality �9 Social Summer 2006, Vol. 25, No. 2, pp. 132-143.
Ferraro, Christopherson, and Douglas 133
cific phobias have used samples of individuals with spider phobia, so it is unclear whether paying more attention to threatening information generalizes to individuals with other phobias (for example, blood phobia). In addition, the Stroop task (the finding that it takes people longer to name the ink color a word is printed in when the word is the name of a competing ink color; the word red printed in green ink) has been used almost exclusively to examine these biases (Chen, Lewin, & Craske, 1996; Thorpe & Salkovskis, 1997; Van den Hout et al., 1997; Watts et al., 1986), making it unclear whether other types of information processing (as measured by other information processing tasks) are disturbed in individuals with specific phobias). Theoretically, individuals with a phobia may require an additional stage of processing and additional time to process information (due to the allocation of cognitive resources), which either slows them down or interferes with their information processing capabilities, as com- pared to individuals without a phobia (see Sternberg, 1969, for a general stage model of information processing).
A notable exception is the work of Sawchuk et al. (1999), who examined informa- tion processing in individuals with a phobia for blood/injury/injection. Individuals with and without a phobia completed both a modified Stroop task and a word stem completion task (a task in which the first three letters of a word are missing and a subject must fill them in . . . . pet for carpet), both of which included medical-related, disgust-related, and neutral stimuli. The individuals with a phobia for blood/injury/ injection completed more medical and disgust word stems correctly than individuals without a phobia, but individuals with a phobia for blood/injury/injection did not process these stimuli the same way on the Stroop task. These results suggest that blood phobia individuals pay more attention to blood-related stimuli than individuals with a spider phobia, as most studies examining Stroop performance in this specific phobia do show color-naming interference (for example, Watts et al., 1986). These results also suggest that type of task used (word stem completion, Stroop) may have an impact how individuals process information.
Results of the lexical decision task (LDT) have been used extensively in both the anxiety and depression literatures (Baldwin & Main, 2001; Siegle, Ingram, & Matt, 2002), although it has yet to be used to examine cognitive biases in phobic and fearful individuals. The LDT requires a speeded response such that participants must decide whether or not a string of letters forms a real English word (cat) or not (blant; Balota, Ferraro, & Connor, 1991). Results from LDTs offer an estimation of semantic memory functioning and structure as well as speed of information processing. Existing results also allow for examination of how specific lexical items are processed and, presum- ably, stored in semantic, or long-term, memory.
Use of the LDT in phobic individuals may provide insight about how these indi- viduals process, store, and ultimately use information and, in turn, how processing this information affects their day-to-day activities. Specifically, if individuals with a pho- bia are more preoccupied with phobia-related information (information related to their phobia), they would show faster response times in a LDT to material related specifi- cally to their phobia and respond slower to information unrelated to their specific phobia. Because phobia-related information may be at a higher threshold initially and
134 Current Psychology / Summer 2006
require little information for activation (because of its relevance to the phobia in- volved), more accurate processing of phobia-related information (e.g., faster and more accurate responses to phobia-related information) may result. The Stroop task does not require a decision component since participants simply name the ink color of stimuli that are presented to them.
Although many LDT studies present subjects with one word at a time for process- ing (Challis & Krane, 1988; Graves, Landis, & Goodglas, 1981; Lorenz & Newman, 2002; Mathews & Milroy, 1994; Olafson & Ferraro, 2001; Strauss, 1983), results tend to differ when more than one word is presented on a given trial. MacLeod and Mathews (1985) found processing differences between high and low anxiety groups when two letter strings (one being a threatening word) were presented simultaneously. Likewise, when a semantic priming paradigm is used in conjunction with a lexical decision task (Meyer & Schvaneveldt, 1971), in which a prime word "dog" appears prior to the presentation of a target word "cat," individuals with high levels of dysphoric mood (not depressed, but in a sad or blue mood) show better processing of depression- related words and positive words in comparison to non-dysphoric subjects (Scott, Mogg, & Bradley, 2001). Apparently, the presentation of "dog" prior to "cat" facili- tates LDT performance to "cat," and responses are faster and more accurate than if "cat" was not preceded by "dog," or if cat was preceded by an unrelated word (chair) or a pseudoword (blant).
Based on the studies mentioned thus far, information processing performance is affected not only by the task employed but also by the type of subject group participat- ing. To remedy some of the issues raised previously [for example, using a limited number of cognitive tasks, such as the Stroop task) and investigating only one type of specific phobia (namely spider phobia)] we recruited blood-fearful individuals, spider- fearful individuals, and nonfearful (control) individuals to participate in two experi- ments. All participants were university undergraduates who had previously been screened for being afraid of blood, afraid of spiders, or not afraid of either blood or spiders and all completed a simple reaction time task (SRT) and a standard LDT to blood-related, spider-related, neutral, positive, and pseudoword stimuli. Because the LDT involves pressing a key (a motor response), we wanted to ensure that our groups were equal on a measure of SRT, or motor processing (see Results section on SRT performance).
Consistent with the fear-congruent memory literature (that is, Bower, 1981), we expected that blood-fearful individuals should process blood-related words faster than spider-related words and spider-fearful individuals should process spider-related words faster than blood-related words. All groups should process pseudowords slower than words, and all groups should process neutral words similarly (Ferraro, 1995).
METHOD
Participants
Participants used in the present study were drawn from two previously performed group-testing sessions (Wenzel et al. 2003) in which undergraduate participants from a
Ferraro, Christopherson, and Douglas 135
large midwestern university (n = 1,702) were administered the 10-item avoidance coping scale of the Spider Phobia Questionnaire (SPQ-AV; Watts & Sharrock, 1984), and the five-item blood/injury scale of the Fear Questionnaire (FQ-B/I; Marks & Mathews, 1979). Individuals meeting the criterion of scoring one standard deviation above the mean on one of these scales (SPQ-AV > 5; FQ-B/I > 16) and below the mean on the other scale were contacted about participating in the study. Individuals scoring one standard deviation above the mean on both inventories were excluded from the study in order to separate samples of relatively pure spider-fearful individuals and relatively pure blood/injury-fearful individuals. Individuals scoring one standard deviation below the mean on both inventories were invited to participate in the study as nonfearful participants. One hundred sixty-six individuals (9.8% of the total sample; M SPQ-AV = 6.0; M FQ-B/I = 3.2) met the criteria to be contacted for participation in the spider-fearful group; 144 individuals (8.5% of the total sample; M SPQ-AV = 1.5; M FQ-B/I = 21.2) met the criteria to be contacted for participating in the blood-fearful group, and 64 individuals (3.8% of the total sample; M SPQ-AV = .8; M FQ-B/I = .2) met the criteria to be contacted for participation in the nonfearful group.
Individuals who met these various criteria were contacted by phone and asked if they wished to participate in the study. In total, 25 blood-fearful individuals, 30 spider- fearful individuals, and 23 nonfearful individuals agreed to participate. All were un- dergraduates who received course or extra credit in exchange for participation.
Materials and Procedure
Following Institutional Review Board approval, participants initially filled out a consent form and a background questionnaire, which included questions about age, education, self-rated health, number of medications they were currently taking, mood (Geriatric Depression Scale; see Ferraro & Chelminski, 1996, who found the GDS-SF correlates highly with the Beck Depression Inventory, 1981), anxiety (State/Trait Anxiety Inventory; Spielberger, Gorsuch, & Lushene 1970), and vocabulary (WAIS-R; Wechsler Adult Intelligence Scale-Revised, Wechsler, 1981). In addition, they again completed the Fear Questionnaire (FQ) and the Spider Phobia Questionnaire (SPQ) mentioned above. Next, participants completed a computer test of simple reaction time (SRT) and a lexical decision task (LDT) constructed using the Micro Experimental Laboratory software (MEL; Schneider, 1988). The temporal resolution of MEL's timer is accurate to the nearest. 1 millisecond.
The SRT consisted of 90 trials. Participants first saw a fixation point (*) presented in the middle of a computer screen for 1,000 milliseconds (ms). This was followed by a stimulus (####), which replaced the fixation point and remained on the screen until participants responded. They were instructed to press the space bar as quickly as they could when they saw it. Of the 90 trials, one third were presented with an SOA (stimulus onset asynchrony) of 500ms, one third had an SOA of 1000ms, and one third had an SOA of 1500ms. This was done to reduce expectancy effects on the part of the participants and is common practice in SRT studies. The SRT took approximately five to 10 minutes to complete.
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TABLE 1 Word Stimuli Used in Lexical Decision Experiment
Note: Words above were taken from Wenzel and Holt (1999). They were equated on frequency of occurrence (Kucera & Francis, 1967), number of letters, and number of syllables. Stimuli were chosen based on an extensive norming procedure, assessing the variables specified above as well as pleasantness, imageability and the extent to which they were related to blood and spiders. Pronounce- able pseudowords (e.g., blant, n = 120) were taken from Kellas, Ferraro, and Simpson (1988) and were equated with word stimuli on number of letters and syllables.
The LDT consisted of 20 spider words, 20 blood words, 40 neutral words, and 40 positive words taken from Wenzel and Holt (1999) and appear in Table 1. Word groups were equated by frequency of occurrence (Kucera & Francis, 1967), number of letters, and number of syllables. Stimuli were chosen based on an extensive norming procedure, assessing the variables specified above as well as pleasantness, imageability and the extent to which they were related to blood and spiders. Pronounceable pseudowords (for example, blant, n = 120) were taken from Kellas, Ferraro, and Simpson (1988) and were equated with word stimuli by number of letters and syllables.
In the LDT, a centrally located fixation point (*) appeared in the middle of the screen for 1,000ms and was replaced by either a word or pseudoword. Each participant received the same random order of words and pseudowords. The word or pseudoword remained on the screen for 1500 ms or until the participant responded. Participants were instructed to respond as quickly and as accurately as possible, pressing the "1" key with the index finger of their left hand if the stimulus was a word and the "0" key with the index finger of their right hand if the stimulus was a pseudoword. We did not counterbalance decision type (word, pseudoword) with hand type (left, right). I f they did not respond within 1,500 ms, a tone sounded and the next trial appeared. This trial was counted as an error. All errors (responding word to pseudoword and vice-versa) resulted in a tone sounding to indicate an error had been made. The response to next trial interval was approximately 1,000 ms. The LDT took approximately 15-20 min- utes to complete. To reduce potential order effects, the presentation of the SRT and the LDT were counterbalanced across participants. In other words, if the SRT and the LDT were presented in the same order to all subjects, poor performance on the LDT could then
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be due to possible fatigue effects from doing that task last in the sequence. Counterbal-
ancing the SRT and LDT reduces this possible alternative interpretation o f the result.
RESULTS
Demographic Information
Table 2 lists demographic information across the three groups. One-way A N O V A s revealed no group differences (Fs < 1.51, ps > .23) regarding age (M -- 20.8) and self- reported health (for example, how you feel in comparison to others your same age, M
= 2.37, where 1 = poor and 5 = excellent). However, nonfearful individuals had higher levels o f education and higher vocabulary scores than fearful individuals. Blood-fear- ful individuals scored higher on the FQ than spider-fearful individuals, who in turn scored higher than nonfearful individuals. In contrast, spider-fearful individuals scored higher than both groups on the SPQ. Thus, scores on the fearfulness measures con-
firmed that group membership was valid (see Table 2). In addition, both groups o f fearful individuals scored higher on measures of general distress, although these scores were not in the clinical range (for example, the scores did not exceed the min imum cut-off value necessary for possible diagnosis).
TABLE 2 Mean (M), Standard Deviation (SD), F Values, p Values, and Differences as a
FQ Tot M 39.9 24.0 12.0 26.45 .01 B>S>N SD 16.5 13.4 8.6
SPQ Tot M 5.8 12.1 4.4 33.35 .01 S>B, S>N SD 2.9 5.1 1.6
Note: B indicates blood-fearful (n = 25); S indicates spider-fearful (n = 30); N indicates nonfearful (n = 23); diffs indicates post-hoc differences; GDS-SF indicates Geriatric Depression Scale-Short Form; WAIS-R indicates Wechsler Adult Intelligence Scale-Revised; FQ indicates Fear Questionnaire; SPQ indicates Spider Phobia Questionnaire; Tot indicates Total.
138 Current Psychology / Summer 2006
SRT/Neutral Word Reaction Time (RT)
A one-way ANOVA was performed on mean SRT performance. Blood-fearful (M SRT = 265ms; SD = 40), spider-fearful (M SRT = 275ms, SD = 54), and nonfearful (M SRT = 278ms, SD = 36) individuals did not differ in a statistically significant way, [F(2, 75) = .53, p = .59], suggesting that simple motor response (key press) did not
differ across the groups.
LDT Performance (R T and Errors)
Table 3 presents reaction time and percent correct error data. A speed/accuracy tradeoff (SATO) was calculated across the three groups to ensure that speed was not traded for accuracy. It is important to consider reaction time measures in the context of accuracy measures because o f the inherent tradeoff individuals display between speed and accuracy (for example, many behaviors are less accurate if completed too fast). To examine this, a correlation between mean RT and mean number (or percent) o f errors was calculated and revealed that as RT increased, so did number o f errors/percent error, r = + .27, p < .01. This pattern suggests that the slower individuals performed on the LDT, the more errors they made and this indicates a SATO was not impacting our LDT data.
TABLE 3 Mean (M) and Standard Deviation (SD, in parenthesis) Reaction Time (and Percent
Errors) on LDT as a Function of Group and Stimulus Type
A 3 (Group: blood-fearful, spider-fearful, nonfearful) x 4 (Stimulus Type: blood, spider, neutral, positive) mixed ANOVA was performed on mean correct RT data excluding pseudowords. Group was a between-subjects factor while Stimulus Type was a within-subjects factor. RT outliers (any RT less than 250 ms or greater than 1,000ms) were removed before analysis, resulting in less than 1% of the original data being removed. The percentage o f data removed from analyses did not differ across the three groups. We initially analyzed medians and derived similar results, so only analyses based on means are presented. We performed various Analyses o f Covariance (because the groups differed significantly on several demographic measures) but these did not change the pattern of results detailed below.
Results revealed no main effect for Group, F(2, 75) = 1.41, p = .25, eta-squared = .04, power = .29. The Group x Stimuli interaction was also not significant, F < 1.0. However, there was a main effect for Stimulus Type, F (3 ,225) = 21.05, p < .01, eta- squared = .22, power = 1.0. Response times for all word stimuli differed from each other (Spider = Positive < Blood < Neutral; ts > 3.80, ps < .05) and participants responded to pseudowords slower than all other word types (ps < .01). We also analyzed LDT performance on the neutral words only across the three groups and a one-way ANOVA revealed no group differences on RTs to neutral words (words devoid of any emotional content related to blood and spiders), F(2, 75) = 1.05, p = .35.
A similar ANOVA was performed on mean number of errors. There was no main effect of Group nor a Group x Stimuli interaction, Fs < 1.0. Again, there was a main effect of Stimulus Type (p < .01), with all stimuli being different from each other (ps < .01) except neutral and positive words (p > .05). As expected, pseudoword (stimuli that look like real words but possess no meaning, like "blant") processing lead to more errors (responding word to pseudoword) than all other stimulus types (ps < .01).
Difference Score Analysis
Although the neutral and positive words were included in the stimulus set to act as filler stimuli, it is possible to subtract Blood-related and Spider-related word RTs from the neutral and positive word RTs to gauge how blood and spider fearful groups process blood-related and spider-related material specifically. Two ANOVAs were performed to examine this. One examined Neutral difference scores (Neutral - -B lo o d , Neutral - -Spider) whereas the other ANOVA examined Positive difference scores (Positive - -Blood , Positive --Spider) . For the Neutral Differences, a 3 (Group) x 2 (Difference) ANOVA resulted in no main effect o f Group or Group x Difference interaction, Fs < 1.0. There was a significant main effect of Difference, F(1, 75) = 14.59, p < .01, eta-squared = .16, power = .97). Specifically, the Neutral - - S p i d e r difference (M = 29.7ms, SD = 38.7) was greater than the Neutral - - B l o o d difference (M = 9.2, SD = 40.9). For the Positive Differences, the ANOVA resulted in, again, no Group main effect or Group x Difference interaction (Fs < 1.0). However, there was a significant main effect of Difference, F ( I , 75) = 14.26, p < .01, eta-squared = .16, power = .96). The Positive - -B lood difference (M = -22.1 ms, SD = 45.9) was greater than the Positive - -Spider difference (M = -1.7, SD = 37.3).
140 Current Psychology / Summer 2006
DISCUSSION
The present study intended to investigate how individuals with specific phobias (spiders, blood) process information that is related to their specific phobia. How these individuals process this information may lead to better models of how various phobias affect information processing, comprehension, and understanding of everyday life. We used a single word lexical decision task and subjects made word-pseudoword deci- sions to words in several categories (blood words, spider words, neutral words, posi- tive words, and pseudowords). We expected blood-fearful individuals to respond faster to blood-related words and spider-fearful individuals to respond faster to spider-related words. The present study found no group main or interaction effects, and all three groups responded faster and more accurately to spider words than to blood and neutral words. Our difference score analysis also yielded non-significant effects based on group membership. As mentioned, these results also suggest that paradigms that are based on semantic-conceptual information processing (like lexical decision) are not sensitive enough to detect group differences in blood and spider phobias. Any array of perceptual and conceptual tasks taken together may be needed to detect these differences.
The lack of group main or interaction effects across LDT and difference score performance is surprising because our data were not compromised by a speed-accu- racy trade-off, speed of processing (as measured by the SRT task), or a lexical pro- cessing effect based on responses to neutral word stimuli. Additionally, word stimuli were equated on several important factors known to affect the LDT, and as in most LDT studies pseudoword stimuli were responded to slowest of all stimulus types. We also ensured that the blood phobic individuals, spider phobic individuals, and control individuals met strict criteria for group membership. We used Analysis of Covariance (ANCOVA) to examine the possible impact of the potentially confounded demo- graphic and psychological variables, which differed across our three groups. Results of this analysis of covariance, however, did not change significantly. Despite these neces- sary control measures, we still found no effects based on group membership.
What do these results mean, despite all the control procedures that were employed? What are the implications of examining information processing in individuals with specific phobias (blood, spider)? One issue relates to why all groups responded faster to spider words than blood words. Even though various word recognition controls were used in the present study (for example, equating word stimuli on several relevant factors), it is possible that another unknown word property may have confounded results especially given the multitude of variables that affect single word lexical deci- sion performance (see Balota et al., 1991).
Another issue is that even though we controlled for various factors associated with presented material, we cannot control for what participants activate in long-term memory when presented with these various stimuli. It may be that certain individuals activate specific information about certain words, while other subjects do not. Depending on which information is activated and in what order may affect long-term memory search and, hence, LDT response time. There is evidence that word recognition is a strategic
Ferraro, Christopherson, and Douglas 141
process and that individuals bring different strategies to how they process words (Ferraro et al., 2003).
The manipulation that was not used in the present experiment that may have been necessary to facilitate group differences was the use of a primed lexical decision task. It may be the case that a no-prime single-stimulus LDT is not a sufficiently powerful enough methodology to detect differences in blood--and spider-phobic individuals. Rather, competing stimuli (for example, presenting more than one stimulus at a time on a given trial or using a priming paradigm) presumably must be present before group differences emerge in these two phobias.
This interpretation is consistent with our earlier discussion of the Stroop task (for example, participants must simultaneously stop processing of specific stimuli while at the same time continue processing of other stimuli). In a typical semantic priming experiment, participants must use the information conveyed by the prime in order to make an accurate and fast decision about the target and do so on each trial. Presum- ably, RTs are faster when the prime is related (dog-cat), rather than unrelated (chair- cat), to the target. In other words, the prime (dog) makes the target (cat) more acces- sible and easier to locate in semantic memory. Theoretically, this faster response time is the result of semantic activation spreading from the prime to the target (Meyer & Schevaneveldt, 1971) thereby making the target more accessible. MacLeod and Mathews (1985) found this to be the case with anxious individuals and a similar pattern may emerge within specific phobia groups as well. Although the present experiment did not test this possibility, it may be the case that performing an experiment that combines single-word LDT and primed LDT may provide the necessary answer to this empirical question.
Several limitations of the present study must be acknowledged. First, our samples were non-clinical (that is, they did not have a diagnosable phobia) and, thus, not diagnosed with the DSM-IV for specific phobias. Second, our samples were relatively small and this could have contributed to the lack of significant effects obtained. The resulting power calculations and effects sizes are relatively small, suggesting more participants should have been tested.
On the other hand, our sample size is in line with many of the other studies cited in this paper and in some cases exceeds the sample sizes reported. Third, we only used one task (LDT) and single-word stimuli. Although many information-processing tasks have been employed in this literature, the present results can only generalize to other single word LDT studies. Likewise, sentences, paragraphs and/or pictorial stimuli could be used in future studies to broaden the scope of the present set of results and be more ecologically valid types of stimuli. Fourth, we did not control for response type (yes, no) and hand used (left, right), although the present methodology is consistent with the vast majority of LDT studies published that do not typically control for these variables. Fifth, other characteristics of the stimuli may have contributed to the effects obtained. We attempted to control for as many relevant variables as possible and still have an adequate number of stimuli. However, a factor (or factors) unknown to us may have produced some of the result patterns. Sixth, and finally, we did show some group
142 Current Psychology / Summer 2006
differences on some of the demographic variables, although ANCOVA failed to con- firm their impact.
Despite these limitations, we have shown that use of the LDT does not adequately distinguish between the information processing patterns associated with the specific phobias of blood and spider. In fact, our results suggest that these two groups process lexical information related to blood and spider in the same fundamental way. This is an important finding because studies published over the last 15-20 years have demon- strated that individuals with specific phobias as well as anxiety disorders process information in such a way that their processing strategies bias them towards threaten- ing stimuli. In fact, studies with these groups using paradigms that measure attentional resource allocation have shown that these individuals tend to direct their attention towards environmental stimuli that are threatening as compared to environmental stimuli that are not threatening.
We believe that future research should attempt to access information processing abilities in these two groups by having them perform several information processing tasks that cover the range of information processing abilities (encoding, comparison, decision, response). Future studies should also examine how subject strategy use af- fects information processing. The application of various information processing tasks to these population groups is critical to ultimately understanding how these groups process information cognitively and what underlying mechanisms are responsible for such processing.
N O T E S
Address for correspondence: F. Richard Ferraro, Department of Psychology, University of North Da- kota, Corwin-Larimore, 319 Harvard Street Stop 8380, Grand Forks, ND 58202-8380. E-mail: [email protected]
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