Multiple distance cues do not prevent systematic biases in reach to grasp movements

The knowledge about the usual size of objects—familiar size—is known to be a taken into account for distance perception. The influence of familiar size on action programming is less clear and has not yet been tested with regard to vergence eye movements. In two experiments, we stereoscopically presented everyday objects, such as a credit card or a package of paper tissues, and varied the distance as specified by binocular disparity and the distance as specified by familiar size. Participants had to fixate the shown object and subsequently reach towards it either with open or with closed eyes. When binocular disparity and familiar size were in conflict, reaching movements revealed a combination of the two depth cues with individually different weights. The influence of familiar size was larger when no visual feedback was available during the reaching movement. Vergence movements closely followed binocular disparity and were largely unaffected by familiar size. In sum, the results suggest that in this experimental setting familiar size is taken into account for programming and executing reaching movements while vergence movements are primarily based on binocular disparity.

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“…This tendency towards the mean was stronger for blind reaches. The same bias, often more pronounced, has been found in other studies [7, 83–85].…”

Section: Discussionsupporting

confidence: 86%

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

Schubert¹,

Jung²,

Helmert³

et al. 2019

PLoS ONE

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“…While applying the MLE model to explain perceptual processing may appear straightforward, some of its core assumptions seem not to be satisfied by human perceptual systems. First, many experiments have shown that texture, motion, and binocular disparity cues generally fail to produce accurate percepts, contrary to the veridicality assumption (Bozzacchi & Domini, 2015;Bozzacchi et al, 2016;Campagnoli et al, 2017;Domini & Braunstein, 1998;Domini & Caudek, 1999;Domini & Caudek, 2003;Egan & Todd, 2015;Fantoni et al, 2010;Kopiske et al, 2019;Liu & Todd, 2004;Norman et al, 2004;Norman et al, 1996;Norman et al, 1995;Perotti et al, 1998;Phillips & Todd, 1996;Tittle et al, 1995;Todd, 2004;Todd & Bressan, 1990;Todd et al, 1998;Todd & Norman, 2003;Todd et al, 2014;Todd et al, 1995;Todd & Thaler, 2010;Todd et al, 2005;Todd et al, 2007;Volcic et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Perceiving Depth from Texture and Disparity Cues: Evidence for a Non-Probabilistic Account of Cue Integration

Kemp

Cesanek

Domini

2022

Preprint

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The fundamental question of how the brain derives 3D information from the inherently ambiguous visual input has been approached during the last two decades with probabilistic theories of 3D perception. Probabilistic models, such as the Maximum Likelihood Estimation (MLE) model, derive from multiple independent depth cues the most probable 3D interpretations. These estimates are then combined by weighing them according to their uncertainty to obtain the most accurate and least noisy estimate. In three experiments we tested an alternative theory of cue integration termed the Intrinsic Constraint (IC) theory. This theory postulates that the visual system does not derive the most probable interpretation of the visual input, but the most stable interpretation amid variations in viewing conditions. This goal is achieved with the Vector Sum model, that represents individual cue estimates as components of a multidimensional vector whose norm determines the combined output. In contrast with the MLE model, individual cue estimates are not accurate, but linearly related to distal 3D properties through a deterministic mapping. In Experiment 1, we measured the cue-specific biases that arise when viewing single-cue stimuli of various simulated depths and show that the Vector Sum model accurately predicts an increase in perceived depth when the same cues are presented together in a combined-cue stimulus. In Experiment 2, we show how Just Noticeable Differences (JNDs) are accounted for by the IC theory and demonstrate that the Vector Sum model predicts the classic finding of smaller JNDs for combined-cue versus single-cue stimuli. Most importantly, this prediction is made through a radical re-interpretation of the JND, a hallmark measure of stimulus discriminability previously thought to estimate perceptual uncertainty. In Experiment 3, we show that biases found in cue-integration experiments cannot be attributed to flatness cues, as assumed by the MLE model. Instead, we show that flatness cues produce no measurable difference in perceived depth for monocular (3A) or binocular viewing (3B), as predicted by the Vector Sum model.

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“…This shows that binocular disparity and stereopsis occurs along the dorsal visual pathway all the way through the regions responsible for visually guided manual action encoding both location in depth and 3D shape. Visual guidance of movement, in principle, requires the derivation of absolute values of object dimensions scaled to the motor plant (e.g., separation of thumb and fingers for grasping; required distance of hand transport for reaching; Glennerster et al, 1996; Kopiske et al, 2018); on the other hand, the 3D shape of an object can be specified fully by only relative depth values. How might this be linked to the difference between the phenomenology of stereopsis and perception of pictorial depth?…”

Section: Discussionmentioning

confidence: 99%

Identifying Cortical Substrates Underlying the Phenomenology of Stereopsis and Realness: A Pilot fMRI Study

et al. 2019

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Viewing a real scene or a stereoscopic image (e.g., 3D movies) with both eyes yields a vivid subjective impression of object solidity, tangibility, immersive negative space and sense of realness; something that is not experienced when viewing single pictures of 3D scenes normally with both eyes. This phenomenology, sometimes referred to as stereopsis, is conventionally ascribed to the derivation of depth from the differences in the two eye’s images (binocular disparity). Here we report on a pilot study designed to explore if dissociable neural activity associated with the phenomenology of realness can be localized in the cortex. In order to dissociate subjective impression from disparity processing, we capitalized on the finding that the impression of realness associated with stereoscopic viewing can also be generated when viewing a single picture of a 3D scene with one eye through an aperture. Under a blocked fMRI design, subjects viewed intact and scrambled images of natural 3-D objects, and scenes under three viewing conditions: (1) single pictures viewed normally with both eyes (binocular); (2) single pictures viewed with one eye through an aperture (monocular-aperture); and (3) stereoscopic anaglyph images of the same scenes viewed with both eyes (binocular stereopsis). Fixed-effects GLM contrasts aimed at isolating the phenomenology of stereopsis demonstrated a selective recruitment of similar posterior parietal regions for both monocular and binocular stereopsis conditions. Our findings provide preliminary evidence that the cortical processing underlying the subjective impression of realness may be dissociable and distinct from the derivation of depth from disparity.

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Multiple distance cues do not prevent systematic biases in reach to grasp movements

Cited by 11 publications

References 46 publications

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

Perceiving Depth from Texture and Disparity Cues: Evidence for a Non-Probabilistic Account of Cue Integration

Identifying Cortical Substrates Underlying the Phenomenology of Stereopsis and Realness: A Pilot fMRI Study

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