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Michael Barnett-Cowan, Gavin Buckingham, Jody Culham; The "Verge-Weight" Illusion. Journal of Vision 2014;14(10):404. doi: 10.1167/14.10.404.
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© ARVO (1962-2015); The Authors (2016-present)
Our expectations of how heavy an object will be allow us to use the appropriate level of force to lift an object without having to rely on sensory feedback. After lifting an object from the verge of a table edge, we noted an appreciable change in the perceived weight of the object from when it was lifted from the table's center. To assess this in the lab, in a between-subjects design we had right-handed participants lift objects with their right hand from either the center, left edge, or right edge of a table, or from a pedestal with the same surface area as the base of the objects. On each trial, participants lifted one of three identically shaped cubes of different mass and reported the perceived weight of the object by magnitude estimation. The results show that observers persistently perceive objects placed at the left or right verge of a table edge as weighing more than those placed at the center of the table or those lifted from a pedestal. Comparing grip force rate of change between the index and thumb revealed force being exerted faster for the digit facing toward the table edge (i.e., index finger for right table edge) but only on the first lifting trial. This unexpected 'verge–weight' illusion (VWI), which was found for all objects tested, persisted long after initial errors in grip force rate had been corrected. Our results suggest that the affordance objects have for falling when placed at the verge of a support surface is used by the human sensorimotor system to apply grip force in an initially protective manner. The persistence of the VMI over successive lifts suggests that the perceived weight of objects remains biased from visual heuristics of object stability.
Meeting abstract presented at VSS 2014
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