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Sensory Input

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, 75006 Paris, France. A. The layman’s view.

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Sensory Input

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  1. NEW EVIDENCE AGAINST A PERCEPTUAL-MOTOR DISSOCIATIONAndrei Gorea &Pedro Cardoso-Leitecollaborator:Florian WaszakLaboratoire Psychologie de la PerceptionCNRS & Paris Descartes UniversityBiomédicale des Saints Pères45 rue des Saints Pères, 75006 Paris, France

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

  3. B. The two pathways view Decision rule not specified Action with or without perceptual awareness Lateral Interactions (implicit) ? dorsal Sensory Input ventral Verbal report aware / not aware Percept. Criterion However… since Goodale & Milner (1992), a whole line of research leans in favor of this other view:

  4. 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.

  5. 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].

  6. 7° 7° NOT Masked Masked (metacontrast) 22.5° S2 S1 S2 S2 S1 RT T I M E Yes/No (SDT) liminar perturbation + Response Times S2 Impératif stim. p = 1 S1 prime/target p variable Hits FA Misses CR ≈ S1: Yes/No? Gorea & Waszak (2004); Waszak & Gorea (2004) Waszak, Cardoso-Leite & Gorea (2007).

  7. Masked (metacontrast) NOT Masked SOA S2 “mask” 52 ms S1 “prime” S2 S2 S1 S1 t 13 ms 36 ms 10 Strong Masking conditions (6 Obs) Not (or weakly) Masked (6 Obs) 0 -10 RTMISS – RTCR RT Gain rel. to CR (ms) -20 RTHIT – RTCR -30 -40 One path – Two decisions/criteria race model with variable reference noise levels. -50 0 1 2 3 4 0 1 2 3 4 d’S1 RTMISS – RTCR Perceptual-motor dissociation? Yes/No Liminar perturbation + RTs RTHIT – RTCR • 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 pleadsagainst a sensory-motor dissociation. d’S1 Waszak, Cardoso-Leite & Gorea (2007)

  8. 2AFC Liminar perturbation + RTs 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); • Non-matched sensory & motor assessments; • Dismissal of the decisional behavior (response criteria); • Stimulation complexity entailing problematic data (d’) analysis

  9. 2AFC perceptual task: • Specify target location (L/R) Motor tasks: • Simple RT  press a key as soon as either S1or S2 is seen; • Choice RT equivalent to the 2AFC perceptual task but performed in a speeded mode. 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 The motor dissociation stand predicts thatRTs should be independent of whether or not perceptual responses are correct.

  10. 430 6 Obs sRT - no S1 410 sRT, nM sRT, M 390 cRT, nM 370 cRT, M Reference sRT to S2 in the absence of S1 350 330 RT (ms) 310 290 270 250 230 Incorrect Correct Perceptual (non-speeded) Responses 2AFC Liminar perturbation + RTs 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; • As expected from our previous data (and model), RT-drop is larger under not-masked than under masked conditions.

  11. Not surprisingly (as predicted by any one-pathway race model), they strongly do. 1.0 p(Perc = Correct) (arcsin) 0.5 y = 0.76x + 0.42 r² = 0.45 nM M 0.0 0.0 0.5 1.0 p(Mot = Correct) (arcsin) One (unreasonable) prediction of the sensory-motor dissociation stand is that speeded (‘Motor’) and delayed (‘Perceptual’) decisions should not correlate. 2AFC Liminar perturbation + RTs In short, the present simplified recast of a main pro-dissociation priming experiment yields data entirely compatible with the non-dissociation view.

  12. 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:

  13. Action Simple RT Choice RT with or without awareness Motor Criterion Sensory Input Speed-Accuracy trade-off Internal noise Mask noise Perceptual Criterion Detection Discrimination Perception aware / not aware One pathway-two decisions SDT race model with variable reference noises

  14. Internal noise Mask noise Perceptual Detection (in non-Masking condition) + Simple RT Motor Criterion: Simple (detection) RT Perceptual Missesdo not exceedthe motor criterion and do not contribute (or contribute little) to simple RTs. Speed-Accuracy trade-off PARTIAL “NON-DISSOCIATION” Perceptual Criterion: Detectionwithout Mask

  15. Internal noise Mask noise Perceptual Detection (in non-Masking condition) + Choice RT Motor Criterion: Choice (discrimination) RT Perceptual Missesdo not exceedthe motor criterion and do not contribute (at all) to choice RTs. Speed-Accuracy trade-off FULL “NON-DISSOCIATION” Perceptual Criterion: Detectionwithout Mask

  16. Internal noise Mask noise Perceptual Discrimination (in Masking condition)+ Simple RT Motor Criterion: Simple (detection) RT Perceptual Missesexceed the motor criterion and do contribute to simple RTs. Speed-Accuracy trade-off FULL “DISSOCIATION” Perceptual Criterion: Discrimination with Mask

  17. Internal noise Mask noise Perceptual Discrimination (in Masking condition) + Choice RT Motor Criterion: Choice (discrimination) RT Perceptual Missespartiallyexceed the motor criterion and do (partially) contribute to choice RTs. Speed-Accuracy trade-off PARTIAL “DISSOCIATION” Perceptual Criterion: Discrimination with Mask

  18. 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.

  19. THANK YOU

  20. Conditional probabilities Not surprisingly (as predicted by any one-pathway race model), they strongly do. One (unreasonable) prediction of the sensory-motor dissociation stand is that speeded (‘Motor’; cRT) and delayed (‘Perceptual’) decisions should not correlate. 2AFC Liminar perturbation + RTs In short, the present simplified recast of a main pro-dissociation priming experiment yields data entirely compatible with the non-dissociation view.

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