NEW EVIDENCE AGAINST A PERCEPTUAL-MOTOR DISSOCIATION
Andrei Gorea & Pedro Cardoso-Leite
collaborator:
Florian Waszak
Laboratoire Psychologie de la PerceptionCNRS & Paris Descartes University
Biomédicale des Saints Pères45 rue des Saints Pères, 75006 Paris, France
Sensory Input
A. The layman’s view
Action
with perceptual awareness
PerceptualDecision
Verbal reportaware / not aware
However… since Goodale & Milner (1992), a whole line of
research leans in favor of this other view:
Sensory Input
Action
with or withoutperceptual awareness
Verbal report
aware / not aware
B. The two pathways view
Lateral Interactions(implicit)
ventral
dorsal
Percept. Criterion
Decision rule not specified
?
The experimental paradigms used to test this dissociation in stroke patients (blind sight, ataxia/agnosia…) and normals (size illusions, congruent / incongruent subliminar priming + masking, comparison of perceptual and motor
latencies…) present a number of methodological problems
and / or
reject this dissociation.
Two variants of a liminar perturbation paradigm (versions of standard priming + mask technique) coupled with perceptual and motor (RT) responses test negatively the perceptual-action dissociation hypothesis:
• Yes/No variant;
• 2AFC variant [a recast of Klotz & Neumann’s (1999) subliminar priming].
Gorea & Waszak (2004); Waszak & Gorea (2004)Waszak, Cardoso-Leite & Gorea (2007).
T I M E
S1
prime/targetp variable
S2
Impératif stim.p = 1
S1: Yes/No?
HitsFAMissesCR
≈
S2S1
7° NOT Masked
S2
22.5°
Masked(metacontrast)
S2S1
7°
Yes/No (SDT) liminar perturbation + Response Times
RT
Waszak, Cardoso-Leite & Gorea (2007)
S1
“prime”
S2
“mask”
t
SOA
13 ms 36 ms
52 ms
-50
-40
-30
-20
-10
0
10
RT
Gai
n r
el.
to C
R (
ms)
S1
S2
NOT Masked
0 1 2 3 4
Not (or weakly) Masked(6 Obs)
d’S1
RTHIT – RTCR
d’S1
S1
Masked(metacontrast)
S2
0 1 2 3 4
Strong Masking conditions(6 Obs)
RTHIT – RTCR
RTMISS – RTCR
RTMISS – RTCR Perceptual-motor
dissociation?
Ye
s/N
o L
imin
ar
per
turb
ati
on
+ R
Ts
One path – Two decisions/criteria race modelwith variable reference noise levels.
The motor system reacts only if
the stimulus is present and
observers are “aware” of it (i.e. only for Hits).
The difference between RTs for Hits and Misses pleads against a sensory-motor dissociation.
a recast of Klotz & Neumann (1999)
A congruent/incongruent priming + backward masking RT task with a ‘0’ d’ prime
Methodological problems:0 d’ assessment
unreliable (theoretically & statistically impossible);
2AFC Liminar perturbation + RTs
Stimulation complexity entailing problematic data (d’) analysis
Non-matched sensory & motor assessments;
Dismissal of the decisional behavior (response criteria);
Stimuli & Paradigm(one trial)
A recast of Klotz & Neumann (1999) into a 2AFC format: No d’=0 requirement: target/’prime’ set at
d’1.5 No congruent/incongruent manipulation;
2A
FC
Lim
inar
pe
rtu
rbat
ion
+ R
Ts
2AFC perceptual task: Specify target location (L/R)
Motor tasks: Simple RT press a key as soon
as either S1 or S2 is seen;
Choice RT equivalent to the 2AFC perceptual task but performed in a speeded mode.
The motor dissociation stand predicts that RTs should be independent of whether or not perceptual responses are correct.
As expected from our previous data (and model), RT-drop is larger under not-masked than under masked conditions.
230
250
270
290
310
330
350
370
390
410
430
Incorrect Correct
Perceptual (non-speeded) Responses
RT
(m
s)
sRT - no S1
sRT, nM
sRT, M
cRT, nM
cRT, M
6 Obs
Reference sRT to S2 in the absence of S1
All 6 Obs show identical trends: when S1 is not seen (incorrect perceptual responses), sRT
are about the same as in the absence of S1;
when S1 is seen (correct perceptual responses), sRT are shortened by about 15 ms and cRT by about 28 ms;
2A
FC
Lim
inar
pe
rtu
rbat
ion
+ R
Ts
One (unreasonable) prediction of the sensory-motor dissociation stand is that speeded (‘Motor’) and delayed (‘Perceptual’) decisions should not correlate.
In short, the present simplified recast of a main pro-dissociation priming experiment yields data entirely compatible with the non-dissociation view.
2A
FC
Lim
inar
pe
rtu
rbat
ion
+ R
Ts Not surprisingly (as predicted by any one-pathway race model), they
strongly do.
y = 0.76x + 0.42
r² = 0.45
0.0
0.5
1.0
0.0 0.5 1.0
p(Mot = Correct) (arcsin)
p(P
erc
= C
orr
ect)
(ar
csin
)
nM
M
These and previous data (Cardoso-Leite, Gorea & Mamassian, 2007;
Cardoso-Leite, Mamassian & Gorea, submitted) suggest that Perception and Action use the same input pathway and relate as follows:
One pathway-two decisions SDT race model with variable reference noises
Simple RT Choice RT
Detection Discrimination
Internal noise Mask noise
Sensory
Input
Perceptual Criterion
Action
Motor Criterion
with or withoutawareness
Perceptionaware / not aware
Speed-Accuracy trade-off
Perceptual Criterion:Detection without Mask
Speed-Accuracy trade-off
Motor Criterion:Simple (detection) RT
Perceptual Detection (in non-Masking condition) + Simple RT
PARTIAL “N
ON-DIS
SOCIATIO
N”
Internal noise Mask noise
Perceptual Misses do not exceed the motor criterion and do not contribute (or contribute little) to simple
RTs.
Speed-Accuracy trade-off
Perceptual Detection (in non-Masking condition) + Choice RT
Perceptual Criterion:Detection without Mask
Motor Criterion:Choice (discrimination) RT
FULL “NON-D
ISSOCIA
TION”
Internal noise Mask noise
Perceptual Misses do not exceed the motor criterion and do not contribute (at
all) to choice RTs.
Perceptual Discrimination (in Masking condition) + Simple RT
Speed-Accuracy trade-off
Perceptual Misses exceed the motor criterion and do contribute to simple RTs.
Motor Criterion:Simple (detection) RT
Perceptual Criterion:Discrimination with Mask
FULL “DIS
SOCIATIO
N”
Internal noise Mask noise
Speed-Accuracy trade-off
Perceptual Discrimination (in Masking condition) + Choice RT
Motor Criterion:Choice (discrimination) RT
Perceptual Misses partially exceed the motor criterion and do (partially) contribute to choice RTs.
Perceptual Criterion:Discrimination with Mask
PARTIAL “D
ISSOCIA
TION”
Internal noise Mask noise
In CONCLUSION
The Perceptual-Action dissociation / non-dissociation issue is resolved by assuming a unique processing stream with distinct perceptual and motor decision criteria whose relationship is modulated by
the stimulation conditions (with or without masking)
and by
the perceptual (detection vs. discrimination) and motor (simple vs. choice RTs) tasks.
THANK YOU
One (unreasonable) prediction of the sensory-motor dissociation stand is that speeded (‘Motor’; cRT) and delayed (‘Perceptual’) decisions should not correlate.
In short, the present simplified recast of a main pro-dissociation priming experiment yields data entirely compatible with the non-dissociation view.
Not surprisingly (as predicted by any one-pathway race model), they strongly do.
0.0
0.2
0.4
0.6
0.8
1.0
0.0 0.2 0.4 0.6 0.8 1.0p(Perc = Correct \ Mot = Incorrect )
p(P
erc
= C
orr
ec
t \
Mo
t =
Co
rre
ct)
not Masked
Masked
Conditional probabilities
2A
FC
Lim
inar
pe
rtu
rbat
ion
+ R
Ts