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Petra Vetter, Bahador Bahrami, Brian Butterworth; Visual enumeration under load: also subitizing needs attention. Journal of Vision 2007;7(9):705. doi: 10.1167/7.9.705.
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© ARVO (1962-2015); The Authors (2016-present)
Traditionally, the enumeration of a small number of items (1 to about 4), referred to as subitizing, has been thought of as a parallel and pre-attentive process, particularly in comparison with the enumeration of larger numerosities. Using a dual-task paradigm, we tested subitizing performance under conditions of reduced attentional resources. Participants were asked to perform a central detection task of either low attentional load (detecting a certain colour) or high attentional load (detecting a certain colour-orientation conjunction). As a secondary task, participants were asked to judge the numerosity of surrounding high contrast gabor patches amongst low contrast distractor patches. Subitizing accuracy was already significantly decreased when visual attention had to be shared between the enumeration task and the low load detection task, but was even more severely impaired when the detection task required a high amount of attentional resources (high load condition). These results reject the traditionally held notion of subitizing as an attention-independent process.
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