Subitizing reflects visuo-spatial object individuation capacity.

Center for Mind/Brain Sciences, University of Trento, Italy.
Cognition (Impact Factor: 3.63). 06/2011; 121(1):147-53. DOI: 10.1016/j.cognition.2011.05.007
Source: PubMed

ABSTRACT Subitizing is the immediate apprehension of the exact number of items in small sets. Despite more than a 100years of research around this phenomenon, its nature and origin are still unknown. One view posits that it reflects a number estimation process common for small and large sets, which precision decreases as the number of items increases, according to Weber's law. Another view proposes that it reflects a non-numerical mechanism of visual indexing of multiple objects in parallel that is limited in capacity. In a previous research we have gathered evidence against the Weberian estimation hypothesis. Here we provide first direct evidence for the alternative object indexing hypothesis, and show that subitizing reflects a domain general mechanism shared with other tasks that require multiple object individuation.

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