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Emilie Shepherd, Frank Durgin; No effect of unitization (connectedness) on the adaptation of perceived number. Journal of Vision 2016;16(12):815. doi: https://doi.org/10.1167/16.12.815.
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© ARVO (1962-2015); The Authors (2016-present)
There is some evidence, for small collections, that perceived number is affected by grouping or unitization of sub-elements. Do these grouping effects extend to large collections and do they affect adaptation to those collections? Here we consider whether using large collections of grouped units rather than separate element alters the adapting power of a collection. Our grouped units were composed by joining four lines ("legs") by means of a circular "body"; collections of these were compared to collections of un-connected lines. If unitization affects adapting power, than adaptation should be less for connected units. But if unitization fails for large collections, then 400 unconnected lines would be equivalent in adaptive power to 100 units composed of 4 lines and a central body. We tested this in two ways. First (N=28), we compared the strength of adaptation from 100 grouped units (adapted on one side of fixation) with the strength of adaptation from 400 unconnected lines (similarly adapted) when assessed with much lower numerosities in the adapted region (e.g, 12, 25, or 50 lines). For all of these numerosities, the average adapting power of 100 grouped units (M = 34% reduction following adaptation) was no different from the adapting power of 400 legs without bodies (M = 35% reduction following adaptation). We next (N=18) asked how adaptation to 100 connected units would affect the perceived numerosity of a field of 200 legs presented in the same location. Once again the effects of adaptation to 100 connected units did not differ from the effect of adapting to 400 unconnected legs in the same location. Adaptation to either of these stimuli reduced the perceived (matched) numerosity for 200 legs by about 25%. These data show that unitization by connectedness in large collections does not seem to modulate the adaptative power of those collections.
Meeting abstract presented at VSS 2016
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