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Melanie Palomares, Loandra Torres, Carly Leonard, Howard Egeth; Does subitizing require attention?. Journal of Vision 2006;6(6):782. doi: 10.1167/6.6.782.
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Simultaneous enumeration of items seems to have two components. Subitizing is the fast and accurate enumeration of 1–3 items while counting is the slow and inaccurate enumeration of more than 3 items. As subitizing seem automatic and effortless, many have posited that it operates preattentively (Trick & Pylyshyn, 1993; Sathian et al., 1999). To directly test this idea, we asked observers to identify a letter (Target 1) and to enumerate dots (Target 2) within a rapid serial visual presentation (RSVP) stream. We varied the number of dots from 0 to 9 and the temporal lag between Target 1 and Target 2 from 0 to 400 ms. If subitizing is preattentive, then enumeration within this range should be immune to the attentional blink, which is the decrease in Target 2 accuracy when the temporal lag between Target 1 and 2 is short (Joseph, Chun and Nakayama, 1997). Interestingly, there was no attentional blink for enumerating 0 or 1 items. More importantly, however, there were small but significant attentional blinks within the subitizing range (2–3 items) as well as within the counting range (4–9 items). Our results suggest that detecting the presence or absence of a single item is preattentive, while enumeration of multiple items within both subitizing and counting range requires attention.
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