NEW EVIDENCE AGAINST A PERCEPTUAL-MOTOR DISSOCIATION Andrei Gorea & Pedro Cardoso-Leite collaborator: Florian Waszak Laboratoire Psychologie de la Perception CNRS & Paris Descartes University Biomédicale des Saints Pères 45 rue des Saints Pères, Paris, France

Sensory Input A. The layman’s view Action with perceptual awareness Perceptual Decision Verbal report aware / not aware

However… since Goodale & Milner (1992), a whole line of research leans in favor of this other view: Sensory Input Action with or without perceptual 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 S 1 prime/target p variable S 2 Impératif stim. p = 1 S 1 : Yes/No? Hits FA Misses CR ≈ S2S2 S1S1  7° NOT Masked S2S2 22.5° Masked (metacontrast) S2S2 S1S1  7° Yes/No (SDT) liminar perturbation + Response Times RT

Waszak, Cardoso-Leite & Gorea (2007) S 1 “prime” S 2 “mask” t SOA 13 ms36 ms 52 ms RT Gain rel. to CR (ms) S1S1 S2S2 NOT Masked Not (or weakly) Masked (6 Obs) d’ S1 RT HIT – RT CR d’ S1 S1S1 Masked (metacontrast) S2S Strong Masking conditions (6 Obs) RT HIT – RT CR RT MISS – RT CR Perceptual- motor dissociation? Yes/No Liminar perturbation + RTs One path – Two decisions/criteria race model with 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; 2AFC Liminar perturbation + RTs 2AFC perceptual task:  Specify target location (L/R) Motor tasks:  Simple RT  press a key as soon as either S 1 or S 2 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. 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; 2AFC Liminar perturbation + RTs

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. 2AFC Liminar perturbation + RTs Not surprisingly (as predicted by any one-pathway race model), they strongly do. y = 0.76x r² = p(Mot = Correct) (arcsin) p(Perc = Correct) (arcsin) 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 RTChoice RT DetectionDiscrimination Internal noiseMask noise Sensory Input Perceptual Criterion Action Motor Criterion with or without awareness Perception aware / 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 “NON-DISSOCIATION” Internal noiseMask 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-DISSOCIATION” Internal noiseMask 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 “DISSOCIATION” Internal noiseMask 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 “DISSOCIATION” Internal noiseMask 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. Conditional probabilities 2AFC Liminar perturbation + RTs

One pathway-two decisions SDT race model with variable reference noises Sensory Input Action with or without perceptual awareness Verbal report aware / not aware ventral? Lateral Interactions Detection C. Present view Motor Criterion Simple RT Percept. Criterion Discrimination (relative to Mask alone) Choice RT Internal noiseMask noise Speed-Accuracy trade-off

One pathway-two decisions SDT race model. Percept. Criterion Simple RTChoice RT DetectionDiscrimination Speed-Accuracy trade-off In the choice/discrimination case, the motor criterion is high but below the ’perceptual’/non-speeded criterion. Perceptual Misses partially exceed the motor criterion and do (partially) contribute to cRTs. In the simple/detection case, both criteria are low and their rank is reversed. Perceptual Misses do not exceed the motor threshold and do not contribute (or contribute less) to sRTs. Masking strength modulates these interferences. Motor Criterion

Percept. Criterion Speed-Accuracy trade-off Motor criterion in the Simple (detection) RT task. Perceptual criterion in the Detection without Mask task. Perceptual Misses do not exceed the motor threshold and do not contribute (or contribute less) to simple RTs. Motor Criterion Simple RT + Perceptual Detection (in non-Masking condition)

Percept. Criterion Speed-Accuracy trade-off Perceptual’ Misses do not exceed the motor threshold and do not contribute to choice RTs. Choice RT + Perceptual Detection (in non-Masking condition) Motor Criterion Perceptual criterion in the Detection without Mask task. Motor criterion in the Choice (discrimination) RT task.

Simple RT + Perceptual Discrimination (in Masking condition) Percept. Criterion Speed-Accuracy trade-off Motor Criterion Motor criterion in the Simple (detection) RT task. Perceptual criterion in the Discrimination with Mask task. Perceptual Misses exceed the motor criterion and do contribute to simple RTs.

Percept. Criterion Speed-Accuracy trade-off Choice RT + Perceptual Discrimination (in Masking condition) Perceptual Misses partially exceed the motor criterion and do (partially) contribute to choice RTs. Motor criterion in the Choice (discrimination) RT task. Motor Criterion Perceptual criterion in the Discrimination with Mask task.