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Visual illusions modify object size estimates for prospective action judgements.
Neuropsychologia. 2018 08; 117:211-221.N

Abstract

How does the eye guide the hand in an ever-changing world? The perception-action model posits that visually-guided actions rely on object size estimates that are computed from an egocentric perspective independently of the visual context. Accordingly, adjusting grip aperture to object size should be resistant to illusions emerging from the contrast between a target and surrounding elements. However, experimental studies gave discrepant results that have remained difficult to explain so far. Visual and proprioceptive information of the acting hand are potential sources of ambiguity in previous studies because the on-line corrections they allow may contribute to masking the illusory effect. To overcome this problem, we investigated the effect on prospective action judgements of the Ebbinghaus illusion, a visual illusion in which the perceived size of a central circle varies according to the size of surrounding circles. Participants had to decide whether they thought they would be able to grasp the central circle of an Ebbinghaus display between their index finger and thumb, without moving their hands. A control group had to judge the size of the central circle relative to a standard. Experiment 1 showed that the illusion affected perceptual and grasping judgements similarly. We further investigated the interaction between visual illusions and grip aperture representation by examining the effect of concurrent motor tasks on grasping judgements. We showed that participants underestimated their ability to grasp the circle when they were squeezing a ball between their index finger and thumb (Experiment 2), whereas they overestimated their ability when their fingers were spread apart (Experiment 3). The illusion also affected the grasping judgement task and modulated the interference of the squeezing movement, with the illusion of largeness enhancing the underestimation of one's grasping ability observed in Experiment 2. We conclude that visual context and body posture both influence action anticipation, and that perception and action support each other.

Authors+Show Affiliations

Psychological Sciences Research Institute, Université catholique de Louvain, Place Cardinal Mercier 10, Louvain-la-Neuve, Belgium. Electronic address: laurie.geers@uclouvain.be.Psychological Sciences Research Institute, Université catholique de Louvain, Place Cardinal Mercier 10, Louvain-la-Neuve, Belgium; Institute of Neuroscience, Université catholique de Louvain, Avenue Mounier 53, Brussels, Belgium. Electronic address: mauro.pesenti@uclouvain.be.Psychological Sciences Research Institute, Université catholique de Louvain, Place Cardinal Mercier 10, Louvain-la-Neuve, Belgium; Institute of Neuroscience, Université catholique de Louvain, Avenue Mounier 53, Brussels, Belgium. Electronic address: michael.andres@uclouvain.be.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

29883576

Citation

Geers, Laurie, et al. "Visual Illusions Modify Object Size Estimates for Prospective Action Judgements." Neuropsychologia, vol. 117, 2018, pp. 211-221.
Geers L, Pesenti M, Andres M. Visual illusions modify object size estimates for prospective action judgements. Neuropsychologia. 2018;117:211-221.
Geers, L., Pesenti, M., & Andres, M. (2018). Visual illusions modify object size estimates for prospective action judgements. Neuropsychologia, 117, 211-221. https://doi.org/10.1016/j.neuropsychologia.2018.06.003
Geers L, Pesenti M, Andres M. Visual Illusions Modify Object Size Estimates for Prospective Action Judgements. Neuropsychologia. 2018;117:211-221. PubMed PMID: 29883576.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Visual illusions modify object size estimates for prospective action judgements. AU - Geers,Laurie, AU - Pesenti,Mauro, AU - Andres,Michael, Y1 - 2018/06/06/ PY - 2018/02/22/received PY - 2018/05/16/revised PY - 2018/06/04/accepted PY - 2018/6/9/pubmed PY - 2019/2/9/medline PY - 2018/6/9/entrez KW - Action KW - Dorsal stream KW - Ebbinghaus illusion KW - Motor imagery KW - Motor interference KW - Perception SP - 211 EP - 221 JF - Neuropsychologia JO - Neuropsychologia VL - 117 N2 - How does the eye guide the hand in an ever-changing world? The perception-action model posits that visually-guided actions rely on object size estimates that are computed from an egocentric perspective independently of the visual context. Accordingly, adjusting grip aperture to object size should be resistant to illusions emerging from the contrast between a target and surrounding elements. However, experimental studies gave discrepant results that have remained difficult to explain so far. Visual and proprioceptive information of the acting hand are potential sources of ambiguity in previous studies because the on-line corrections they allow may contribute to masking the illusory effect. To overcome this problem, we investigated the effect on prospective action judgements of the Ebbinghaus illusion, a visual illusion in which the perceived size of a central circle varies according to the size of surrounding circles. Participants had to decide whether they thought they would be able to grasp the central circle of an Ebbinghaus display between their index finger and thumb, without moving their hands. A control group had to judge the size of the central circle relative to a standard. Experiment 1 showed that the illusion affected perceptual and grasping judgements similarly. We further investigated the interaction between visual illusions and grip aperture representation by examining the effect of concurrent motor tasks on grasping judgements. We showed that participants underestimated their ability to grasp the circle when they were squeezing a ball between their index finger and thumb (Experiment 2), whereas they overestimated their ability when their fingers were spread apart (Experiment 3). The illusion also affected the grasping judgement task and modulated the interference of the squeezing movement, with the illusion of largeness enhancing the underestimation of one's grasping ability observed in Experiment 2. We conclude that visual context and body posture both influence action anticipation, and that perception and action support each other. SN - 1873-3514 UR - https://www.unboundmedicine.com/medline/citation/29883576/Visual_illusions_modify_object_size_estimates_for_prospective_action_judgements_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0028-3932(18)30269-0 DB - PRIME DP - Unbound Medicine ER -