The same object and at least three different grip apertures

Campagnoli, Carlo; Volcic, Robert; Domini, Fulvio

doi:10.1167/12.9.429

Cited by 7 publications

(5 citation statements)

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“…As soon as the hand was close enough to the target object, the vision of the hand allowed participants to guide their fingers onto the physical surface of the object. This is in line with previous evidence showing that what ensures a successful grasp movement is a combination of online visual control during a given trial and sensorimotor error-prediction to adjust the movements of the following trials (Bozzacchi et al, 2014, 2016; Bozzacchi & Domini, 2015; Campagnoli & Domini, 2019; Campagnoli et al, 2012; Campagnoli et al, 2015; Campagnoli et al, 2017; Cesanek et al, 2018; Cesanek & Domini, 2017; Foster et al, 2011; Volcic et al, 2013; Volcic & Domini, 2014, 2016).…”

Section: Discussionsupporting

confidence: 92%

Explicit and implicit depth-cue integration: evidence of systematic biases with real objects

Campagnoli

Hung

Domini

2021

Preprint

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In a previous series of experiments using virtual stimuli, we found evidence that 3D shape estimation agrees to a superadditivity rule of depth-cue combination. According to this rule, adding depth cues leads to greater perceived depth magnitudes and, in principle, to depth overestimation. The mechanism underlying the superadditivity effect can be fully accounted for by a normative theory of cue integration, through the adaptation of a model of cue integration termed the Intrinsic Constraint (IC) model. As for its nature, it remains unclear whether superadditivity is a byproduct of the artificial nature of virtual environments, causing explicit reasoning to infiltrate behavior and inflate the depth judgments when a scene is richer in depth cues, or the genuine output of the process of depth-cue integration. In the present study, we addressed this question by testing whether the IC model's prediction of superadditivity generalizes beyond VR environments to real world situations. We asked participants to judge the perceived 3D shape of cardboard prisms through a matching task. To assay the potential influence of explicit control over those perceptual estimates, we also asked participants to reach and hold the same objects with their fingertips and we analyzed the in-flight grip size during the reaching. Using physical objects ensured that all visual information was fully consistent with the stimuli's 3D structure without computer-generated artifacts. We designed a novel technique to carefully control binocular and monocular 3D cues independently from one another, allowing to add or remove depth information from the scene seamlessly. Even with real objects, participants exhibited a clear superadditivity effect in both explicit and implicit tasks. Furthermore, the magnitude of this effect was accurately predicted by the IC model. These results confirm that superadditivity is an inherent feature of depth estimation.

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Section: Discussionsupporting

confidence: 92%

Explicit and implicit depth-cue integration: evidence of systematic biases with real objects

Campagnoli

Hung

Domini

2021

Preprint

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“…In previous work, we found that when the vision of the hand is prevented during grasping, the reaching endpoint reveals systematic biases in the estimation of egocentric distance (Bozzacchi, Volcic, & Domini, 2014, 2016Campagnoli et al, 2012). Moreover, we have also shown that both perceptual judgments and reach-to-grasp actions reveal systematic depth underconstancy (Bozzacchi & Domini, 2015;Foster, Fantoni, Caudek, & Domini, 2011;Volcic et al, 2013).…”

Section: Does Vision For Action Share the Same 3d Representation As Vmentioning

confidence: 59%

Stereovision for action reflects our perceptual experience of distance and depth

2017

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Binocular vision is widely recognized as the most reliable source of 3D information within the peripersonal space, where grasping takes place. Since grasping is normally successful, it is often assumed that stereovision for action is accurate. This claim contradicts psychophysical studies showing that observers cannot estimate the 3D properties of an object veridically from binocular information. In two experiments, we compared a front-to-back grasp with a perceptual depth estimation task and found that in both conditions participants consistently relied on the same distorted 3D representation. The subjects experienced (a) compression of egocentric distances: objects looked closer to each other along the z-axis than they were, and (b) underconstancy of relative depth: closer objects looked deeper than farther objects. These biases, which stem from the same mechanism, varied in magnitude across observers, but they equally affected the perceptual and grasping task of each subject. In a third experiment, we found that the visuomotor system compensates for these systematic errors, which are present at planning, through online corrections allowed by visual and haptic feedback of the hand. Furthermore, we hypothesized that the two phenomena would give rise to estimates of the same depth interval that are geometrically inconsistent. Indeed, in a fourth experiment, we show that the landing positions of the grasping digits differ systematically depending on whether they result from absolute distance estimates or relative depth estimates, even when the targeted spatial locations are identical.

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“…This assumption, however, conflicts with empirical evidence showing that stereo information alone does not yield veridical 3D shape estimates for both perceptual judgments Brenner & van Damme, 1999;Hibbard & Bradshaw, 2003;Johnston, 1991;Todd, Tittle, & Norman, 1995) and the execution of a grasping movement (Campagnoli, Croom, & Domini, 2017;Campagnoli, Volcic, & Domini, 2012). Here we investigate whether these biases are the result of (1) a general inaccurate metric analysis of the visual scene that action overcomes through online control or (2) the impoverished visual stimulation of displays conveying exclusively stereo information.…”

mentioning

confidence: 89%

Does depth-cue combination yield identical biases in perception and grasping?

Campagnoli¹,

Domini²

2019

Journal of Experimental Psychology: Human Perception and Perfor

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Grasping critically depends on stereo information. We previously found that binocular disparities yield a distorted visual space, in which objects close to the observer are grasped and perceived as if they were more elongated than farther objects. Such lack of shape constancy results from the inaccurate estimate of the viewing distance, which affects the estimated depth-to-width ratio of an object. This is because (1) depth from binocular disparities scales with the square of the distance and (2) width from retinal size scales linearly with distance. Conversely, depth from monocular cues (i.e., motion and texture gradients) scales linearly with distance, hence the overall shape from these signals should not be affected by errors in egocentric estimates of object location. We therefore reasoned that adding these cues to stereo information should improve shape constancy. Contrary to expectations, in four experiments we found that stereo-texture and stereo-motion stimuli appeared even more distorted than stereo stimuli. More remarkably, results revealed that grasping execution showed identical biases, which were corrected only late in the movement through online control mechanisms, but only if both grasping digits could be visually guided on their respective contact locations. On the contrary, when the index was occluded by the object, biases in shape estimation continued to affect grasping execution until movement completion. Moreover, while the initial part of the grasp showed evidence of collision avoidance, a control experiment suggested that the above biases could have emerged as early as at movement planning, consistent with previous evidence.

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The same object and at least three different grip apertures

Cited by 7 publications

References 0 publications

Explicit and implicit depth-cue integration: evidence of systematic biases with real objects

Explicit and implicit depth-cue integration: evidence of systematic biases with real objects

Stereovision for action reflects our perceptual experience of distance and depth

Does depth-cue combination yield identical biases in perception and grasping?

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