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Richard Held; On maintaining crossmodal identity. Journal of Vision 2009;9(8):702. doi: 10.1167/9.8.702.
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© ARVO (1962-2015); The Authors (2016-present)
The Prakash group reported (J. Vision, 2008,8,23) that the congenitally blind person who gains sight initially fails to identify seen objects with their felt versions: a negative answer to the Molyneux question. However, s(he) succeeds in doing so after a few days of sight. We argue that this rapid learning resembles that of adaptation to rearrangement in which the experimentally-produced separation of seen and felt perceptions of objects are very rapidly reunited by the process called capture. Moreover, we hypothesize that the original ability to identify objects across modalities by the neonate is assured by the same process.
The identification of seen with felt representations and vice versa requires that both be attributable to a single object. Otherwise they are independent and unrelated. How is this unity achieved? The prime condition for unity is spatiotemporal superposition. The normally perceived object is palpable at the location and time that it is seen. For the blind person the seen aspect is of course absent. When vision is acquired the temporal superposition of seen and felt holds but not necessarily the spatial superposition. But, as in prism adaptation, the simultaneity of seen and felt activation should produce spatial superposition by capture.
Analyzing the vast number of rearrangement experiments - optical, electronic, and mechanical - the essential condition for adaptation is the production of spatial discrepancy between the two modes: visual and haptic. With a few exceptions, that prove the rule, temporal superposition of visual and haptic signals remains (simultaneity of brief signals and synchroneity of extended signals) and appears to be the engine of adaptation. Desynchronization of these signals either reduces or eliminates adaptation. Capture, which requires only brief exposure to the generating conditions, appears to be the prototype of the adaptation process.
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