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Lana M. Trick, Elizabeth Orr; The role of object properties in item individuation: The effects of item heterogeneity and change. Journal of Vision 2006;6(6):776. doi: 10.1167/6.6.776.
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© ARVO (1962-2015); The Authors (2016-present)
Item individuation is the ability to consider an item as an individual, and it is necessary if a person is to attend, foveate, or touch a specific item among others. At present it is unclear what role (if any) object properties play in item individuation. One way to investigate individuation is to use the visual enumeration task. Enumeration (determining how many items there are) requires individuation because accurate response requires that each item be considered once and only once. It has long been known that there are differences between enumerating small and large numbers of items. Specifically, when there are 1–4 items, a rapid (40–100 ms/item), accurate, effortless, process called subitizing is used. In contrast, when there are larger numbers of items, a slow (200–350 ms/item), effortful, error-prone process called counting is employed. In a series of studies, the role of object properties in individuation was evaluated by having participants enumerate 1–9 items of various types. In the first, participants enumerated items that were either homogeneous or heterogeneous in their properties. In the second, participants enumerated 1–9 items, but the items constantly changed their properties, their position, or both while being enumerated. Item heterogeneity and property change have different effects depending on the number of items. This effect was interpreted as it relates to recent theories of visual-spatial enumeration and Pylyshyn's (1989) FINST hypothesis.
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