Bimanual Grasping Adheres to Weber's Law

Hesse, Constanze; Harrison, Róisín Elaine; Giesel, Martin; Schenk, Thomas

doi:10.1177/20416695211054534

Cited by 5 publications

(3 citation statements)

References 48 publications

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“…Here we found that actions obey Weber's law. The SD of the final inter-finger separation increased as a function of the inter-target distance, with a slope ranging from 0.012 to 0.038, in line with the classic and modern literature on Weber's law (e.g., Bhatia et al, 2022;Derzsi & Volcic, 2023;Fechner, 1860;Hesse et al, 2021;McKee & Welch, 1992;Teghtsoonian, 1971).…”

Section: Discussionsupporting

confidence: 83%

“…When this non-linear scaling is appropriately considered, Weber's law can be detected even in grasping movements. Moreover, when other variables than MGA are considered, Weber's law is regularly observed (e.g., Derzsi & Volcic, 2023;Hesse et al, 2021). For instance, Derzsi and Volcic (2023) found that to achieve stable grasps on differently sized objects the SD of grasp contact positions increases as a function of object size, coherently with Weber's law.…”

Section: Discussionmentioning

confidence: 81%

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Actions obey Weber’s law when precision is evaluated at goal attainment

Camponogara,

Volcic

2024

Preprint

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Weber’s law, the psychophysical principle stating that the just noticeable difference (JND), which is inversely related to sensory precision, increases proportionally with the magnitude of a stimulus, impacts all domains of human perception, but it is violated in visually guided grasping actions. The underlying reasons for this dissociation between perception and action are still debated, and various hypotheses have been put forward, including a different coding of visual size information for perception and action, the use of positional information to guide grasping, biomechanical factors, or sensorimotor calibration. To contrast these hypotheses, we investigated Weber’s law in a new action task, the two-finger pointing task. Participants reached and touched two targets positioned at different distances apart by using their index finger and thumb. Consistent with Weber’s law, we found that the standard deviation (SD) of the final inter-finger separation, serving as a measure analogous to the JND, increased with larger inter-target distances. These findings suggest that, when considering measures strongly related with the attainment of the action goal, Weber’s law is regularly at play.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 81%

Actions obey Weber’s law when precision is evaluated at goal attainment

Camponogara,

Volcic

2024

Preprint

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“…All these factors should have, if anything, favored the emergence of the perception-action dissociation. The range of sizes used for our objects was also not critical as similar ranges have been already used to study Weber’s law (Ganel et al, 2017; Hesse et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Not only perception but also grasping actions can obey Weber’s law

Derzsi

Volcic

2022

Preprint

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Weber's law, the principle that the uncertainty of perceptual estimates increases proportionally with object size, is regularly violated when considering the uncertainty of the grip aperture during grasping movements. The origins of this perception-action dissociation are debated and are attributed to various reasons, including different coding of visual size information for perception and action, biomechanical factors, the use of positional information to guide grasping, or, sensorimotor calibration. Here, we contrasted these accounts and compared perceptual and grasping uncertainties by asking people to indicate the visually perceived center of differently sized objects (Perception condition) or to grasp and lift the same objects with the requirement to achieve a balanced lift (Action condition). We found that the variability (uncertainty) of contact positions increased as a function of object size in both perception and action. The adherence of the Action condition to Weber's law and the consequent absence of a perception-action dissociation contradict the predictions based on different coding of visual size information and sensorimotor calibration. These findings provide clear evidence that human perceptual and visuomotor systems rely on the same visual information and suggest that the previously reported violations of Weber's law in grasping movements should be attributed to other factors.

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Grasping tiny objects

Giesel,

De Filippi,

Hesse

2024

Psychological Research

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In grasping studies, maximum grip aperture (MGA) is commonly used as an indicator of the object size representation within the visuomotor system. However, a number of additional factors, such as movement safety, comfort, and efficiency, might affect the scaling of MGA with object size and potentially mask perceptual effects on actions. While unimanual grasping has been investigated for a wide range of object sizes, so far very small objects (<5 mm) have not been included. Investigating grasping of these tiny objects is particularly interesting because it allows us to evaluate the three most prominent explanatory accounts of grasping (the perception-action model, the digits-in-space hypothesis, and the biomechanical account) by comparing the predictions that they make for these small objects. In the first experiment, participants ($$N=26$$ N = 26 ) grasped and manually estimated the height of square cuboids with heights from 0.5 to 5 mm. In the second experiment, a different sample of participants ($$N=24$$ N = 24 ) performed the same tasks with square cuboids with heights from 5 to 20 mm. We determined MGAs, manual estimation apertures (MEA), and the corresponding just-noticeable differences (JND). In both experiments, MEAs scaled with object height and adhered to Weber’s law. MGAs for grasping scaled with object height in the second experiment but not consistently in the first experiment. JNDs for grasping never scaled with object height. We argue that the digits-in-space hypothesis provides the most plausible account of the data. Furthermore, the findings highlight that the reliability of MGA as an indicator of object size is strongly task-dependent.

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Bimanual Grasping Adheres to Weber's Law

Cited by 5 publications

References 48 publications

Actions obey Weber’s law when precision is evaluated at goal attainment

Actions obey Weber’s law when precision is evaluated at goal attainment

Not only perception but also grasping actions can obey Weber’s law

Grasping tiny objects

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