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Guido Maiello, Vivian Paulun, Lina Klein, Roland Fleming; The Sequential-Weight Illusion. Journal of Vision 2018;18(10):93. doi: https://doi.org/10.1167/18.10.93.
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We report a perceptual illusion in which the perceived weight of an object appears to change depending on whether a previously manipulated object was lighter or heavier. Two equally sized objects (12.5×2.5×2.5cm), a light wooden object (50g) and a heavy object made of brass (670g), were placed in front of a participant. The participant briefly picked up the wooden object and placed it back down. The participant then picked up the brass object and placed it back down. Finally, the participant picked up the wooden object once more. Strikingly, the wooden object appeared to have lost a substantial amount of weight (-37% median change in weight rating, N=25, p= 0.000010). The illusion worked for the opposite sequence of weight ordering as well: a heavy object appeared to become approximately 11% heavier after picking up a light object (N=10, p=0.010). The illusion is likely related to the interaction between short term motor adaptation and the violation of sensorimotor expectations [Polanen and Davare, 2015]. The forces applied at the fingertips when grasping an object are biased towards those required to grasp the previous object. When fingertip forces do not match the current object weight, online motor corrections rescale both force control and weight estimation. Because our brain must integrate visual and sensorimotor representations to plan our movements, we asked whether visual cues to weight play a role in this illusion. We had participants rate the perceived weight of the alternating heavy and light objects with only sensorimotor or both visual and sensorimotor cues to weight. The strength of the illusion was not modulated by the presence/absence of visual cues (N=35, p=0.55). Thus, our findings demonstrate that visual cues are not integrated with sensorimotor cues during online updating of perceived object weight.
Meeting abstract presented at VSS 2018
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