Perception of area, volume, and weight

Abstract

Countless everyday actions require us to estimate the size and weight of objects that come in various combinations of shape, material, and density. Humans are highly skilled at using different sources of perceptual information, as well as prior experience, to estimate size and weight, and regularly use this information to prepare action. For example, visual estimation of an object’s size and material are used to infer its weight, and thus to prepare the correct forces to pick the object up. However, several aspects of these interrelated human perceptual abilities are subject to poorly understood biases. For example, in size perception, surfaces and objects appear larger or smaller depending on their shape. In weight perception, smaller objects feel heavier than same-weight larger objects (the ‘size-weight illusion’). In this thesis, I explore biases in size and weight perception to broaden the understanding of these fundamental features of human perception. In Chapter 1, I (i) review the literature on biases in area, volume, and weight perception; (ii) highlight how we still lack an accurate understanding of how we perceive the area of surfaces, or volume of objects of different shape, and (iii) how the relationship between perceived volume, weight, and density is still unclear; (iv) identify key questions in each of these areas, addressed in the empirical work presented in the following chapters (2–4). In Chapter 2, I provide a comprehensive account of shape-related biases in area perception and propose a model that quantifies known biases (previously described in qualitative terms), and extends to novel stimuli. In Chapter 3, I provide a quantitative model that predicts biases in perceived weight in the size-weight illusion and generalises to other variations in object size / weight / density. In Chapter 4, I provide an account of the influence of shape in volume and weight perception (the ‘shape-weight illusion’), and provide the first report of the sensorimotor correlates (finger forces and torques for grasping and lifting the objects) of these biases. Findings from the three empirical chapters are discussed together in Chapter 5 within the broader context of the literature reviewed in Chapter 1.

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Identifiers

ORCID for Veronica Pisu: orcid.org/0000-0002-2717-4874

ORCID for Wendy Adams: orcid.org/0000-0002-5832-1056

ORCID for Erich Graf: orcid.org/0000-0002-3162-4233

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