title: Differential effects of delay upon visually and haptically guided grasping and perceptual judgments.
abstract: Experiments with visual illusions have revealed a dissociation between the systems that mediate object perception and those responsible for object-directed action. More recently, an experiment on a haptic version of the visual size-contrast illusion has provided evidence for the notion that the haptic modality shows a similar dissociation when grasping and estimating the size of objects in real-time. Here we present evidence suggesting that the similarities between the two modalities begin to break down once a delay is introduced between when people feel the target object and when they perform the grasp or estimation. In particular, when grasping after a delay in a haptic paradigm, people scale their grasps differently when the target is presented with a flanking object of a different size (although the difference does not reflect a size-contrast effect). When estimating after a delay, however, it appears that people ignore the size of the flanking objects entirely. This does not fit well with the results commonly found in visual experiments. Thus, introducing a delay reveals important differences in the way in which haptic and visual memories are stored and accessed.
authors.affiliation: Department of Psychology, University of Western Ontario, London, ON, Canada. cpettypi@uwo.ca
authors.forename: Charles E
authors.initials: CE
authors.lastname: Pettypiece
authors.forename: Jody C
authors.initials: JC
authors.lastname: Culham
authors.forename: Melvyn A
authors.initials: MA
authors.lastname: Goodale
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D009043:Motor Activity; D013028:Space Perception; D013647:Task Performance and Analysis; D013997:Time Factors; D055698:Touch Perception; D014796:Visual Perception; D055815:Young Adult