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Vivian Paulun, Gavin Buckingham, Karl Gegenfurtner, Roland Fleming, Melvyn Goodale; Modulation of the Material-Weight Illusion in objects made of more than one material. Journal of Vision 2015;15(12):1156. doi: 10.1167/15.12.1156.
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© 2017 Association for Research in Vision and Ophthalmology.
Knowledge about the material properties of objects is essential for successful manual interactions. Vision can provide useful information about features such as weight or friction even before interaction, allowing us to prepare the action appropriately, e.g. adjusting initial forces applied to an object when lifting it. But visual information can also alter multisensory perception of object properties during interaction. When violated, visually-inferred expectations can result in perceptual illusions such as the material-weight illusion (MWI). In this illusion, an object that appears to be made of a low-weight material (e.g., polystyrene) feels heavier than an equally-weighted object of a heavier-looking material (e.g., wood). However, objects are often made of more than one material. Thus, in the present study, we investigated the perceived heaviness of symmetrical objects consisting of two halves, which appeared to be made of different materials: polystyrene, wood, or stone. The true mass of these bipartite objects was identical (400g) and evenly distributed around their geometric centre. Thus, the objects and their halves were visually distinct, but identical in terms of their weight and mass distribution. Participants were asked to lift the objects by a small handle attached centrally, while forces and torques were recorded. Additionally, they were asked to report the perceived weight of both halves of the objects. The visual appearance did indeed alter perceived heaviness. Although estimates of heavier and lighter portions of the objects converged after lifting the objects, the heavier-looking materials in our bipartite objects were still perceived as heavier than the lighter-looking materials. Again, prior expectations appear to affect the perception, but in a direction opposite to that of the MWI. Despite the effects of the visual appearance on perceived heaviness, no corresponding effects were observed on forces or torques.
Meeting abstract presented at VSS 2015
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