Visual illusions modify object size estimates for prospective action judgements

Geers, Laurie; Pesenti, Mauro; Andres, Michaël

doi:10.1016/j.neuropsychologia.2018.06.003

“…by increasing the apparent hand size, size perception was altered as well ([18], but see also [19]). Similarly, the judged ability whether a participant could grasp an object was altered when changing grip aperture by squeezing a ball or spreading the fingers [20]. While this study found an effect on graspability judgements, it did not find effects on size judgements.…”

Section: Introductionmentioning

confidence: 63%

Grasp Aperture Corrections in Reach-to-Grasp Movements Do Not Alter Size Perception

Polanen

¹

2021

Preprint

0

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When grasping an object, the opening between the fingertips (grip aperture) scales with the size of the object. If an object changes in size, the grip aperture has to be corrected. In this study, it was investigated whether such corrections would influence the perceived size of objects. The grasping plan was manipulated with a preview of the object, after which participants initiated their reaching movement without vision. In a minority of the grasps, the object changed in size after the preview and participants had to adjust their grasping movement. Visual feedback was manipulated in two experiments. In experiment 1, vision was restored during reach and both visual and haptic information was available to correct the grasp and lift the object. In experiment 2, no visual information was provided during the movement and grasps could only be corrected using haptic information. Participants made reach-to-grasp movements towards two objects and compared these in size. Results showed that participants adjusted their grasp to a change in object size from preview to grasped object in both experiments. However, a change in object size did not bias the perception of object size or alter discrimination performance. In experiment 2, a small perceptual bias was found when objects changed from large to small. However, this bias was much smaller than the difference that could be discriminated and could not be considered meaningful. Therefore, it can be concluded that the planning and execution of reach-to-grasp movements do not affect the perception of object size.

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“…A different relation between vision and proprioception due to the adaptation might have possibly led to altered manual size estimations. The other study [ 20 ] only found effects of grip aperture alterations on graspability of objects, not on size perception. Since only size perception was measured in the present study, it seems that a judgement that is more related to movement kinematics, i.e.…”

Section: Discussionmentioning

confidence: 96%

“…Recent studies suggested that altered grip apertures could affect the manual estimation of size [ 21 ] or the estimated graspability of the object [ 20 ]. The former study used an adaptation paradigm in virtual reality to alter the grip aperture.…”

Section: Discussionmentioning

confidence: 99%

“…by increasing the apparent hand size, size perception was altered as well ([ 18 ], but see also [ 19 ]). Similarly, in another study, participants had to judge whether they were able to grasp an object with one hand while their grip aperture was altered by squeezing a ball or spreading their fingers [ 20 ]. While this study found differences in graspability judgements between the two tasks, it did not find effects on size judgements.…”

Section: Introductionmentioning

confidence: 99%

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Grasp aperture corrections in reach-to-grasp movements do not reliably alter size perception

Polanen

¹

2021

PLoS ONE

1

0

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When grasping an object, the opening between the fingertips (grip aperture) scales with the size of the object. If an object changes in size, the grip aperture has to be corrected. In this study, it was investigated whether such corrections would influence the perceived size of objects. The grasping plan was manipulated with a preview of the object, after which participants initiated their reaching movement without vision. In a minority of the grasps, the object changed in size after the preview and participants had to adjust their grasping movement. Visual feedback was manipulated in two experiments. In experiment 1, vision was restored during reach and both visual and haptic information was available to correct the grasp and lift the object. In experiment 2, no visual information was provided during the movement and grasps could only be corrected using haptic information. Participants made reach-to-grasp movements towards two objects and compared these in size. Results showed that participants adjusted their grasp to a change in object size from preview to grasped object in both experiments. However, a change in object size did not bias the perception of object size or alter discrimination performance. In experiment 2, a small perceptual bias was found when objects changed from large to small. However, this bias was much smaller than the difference that could be discriminated and could not be considered meaningful. Therefore, it can be concluded that the planning and execution of reach-to-grasp movements do not reliably affect the perception of object size.

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“…Specifically, Linkenauger and colleagues (2011) reported that object size perception can be influenced by the motor action capacity upon the object [ 23 ]. Nonetheless, later studies debated these suggestions [ 24 , 25 ], arguing that these findings may be constrained by the size-contrast illusion [ 25 , 26 ], which is known to be capable of affecting both size perception and grasping judgments [ 27 ]. Based on real physical targets seen in a virtual environment, changes in size perception have been reported [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

Horizontal target size perturbations during grasping movements are described by subsequent size perception and saccade amplitude

Diez

¹

,

Bosco

²

,

Fattori

³

et al. 2022

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Perception and action are essential in our day-to-day interactions with the environment. Despite the dual-stream theory of action and perception, it is now accepted that action and perception processes interact with each other. However, little is known about the impact of unpredicted changes of target size during grasping actions on perception. We assessed whether size perception and saccade amplitude were affected before and after grasping a target that changed its horizontal size during the action execution under the presence or absence of tactile feedback. We have tested twenty-one participants in 4 blocks of 30 trials. Blocks were divided into two experimental tactile feedback paradigms: tactile and non-tactile. Trials consisted of 3 sequential phases: pre-grasping size perception, grasping, and post-grasping size perception. During pre- and post-phases, participants executed a saccade towards a horizontal bar and performed a manual size estimation of the bar size. During grasping phase, participants were asked to execute a saccade towards the bar and to make a grasping action towards the screen. While grasping, 3 horizontal size perturbation conditions were applied: non-perturbation, shortening, and lengthening. 30% of the trials presented perturbation, meaning a symmetrically shortened or lengthened by 33% of the original size. Participants’ hand and eye positions were assessed by a motion capture system and a mobile eye-tracker, respectively. After grasping, in both tactile and non-tactile feedback paradigms, size estimation was significantly reduced in lengthening (p = 0.002) and non-perturbation (p<0.001), whereas shortening did not induce significant adjustments (p = 0.86). After grasping, saccade amplitude became significantly longer in shortening (p<0.001) and significantly shorter in lengthening (p<0.001). Non-perturbation condition did not display adjustments (p = 0.95). Tactile feedback did not generate changes in the collected perceptual responses, but horizontal size perturbations did so, suggesting that all relevant target information used in the movement can be extracted from the post-action target perception.

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Visual illusions modify object size estimates for prospective action judgements

Cited by 6 publications

References 46 publications

Grasp Aperture Corrections in Reach-to-Grasp Movements Do Not Alter Size Perception

Grasp Aperture Corrections in Reach-to-Grasp Movements Do Not Alter Size Perception

Grasp aperture corrections in reach-to-grasp movements do not reliably alter size perception

Horizontal target size perturbations during grasping movements are described by subsequent size perception and saccade amplitude

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