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Katherine Bettencourt, David Somers; Correlations between visual short-term memory and attentional capacity limits. Journal of Vision 2008;8(6):862. doi: 10.1167/8.6.862.
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Both attention and visual short-term memory (VSTM) appear to be limited in capacity by the same underlying mechanisms. Both have shown capacity limits of 4 ± 1 objects (Pylyshyn and Storm, 1988; Yantis, 1992; Cowan 2001; Scholl and Xu, 2001; Luck and Vogel, 1997) and the inferior parietal sulcus (IPS) activates in a capacity limited manner for both processes. However, these findings have been for group averaged data, and both attention and VSTM capacities show large individual differences, with individual subject capacities ranging from 2–5 objects (Oksama and Hyönä, 2004; Vogel and Machizawa, 2004). Thus, it is unknown whether the capacities are actually interrelated, or are simply a coincidence of averaging groups of subjects together. In order to examine whether these capacities are truly related, we compared individual subject's capacities on both an attentional and VSTM task completed in the same testing session. We used a multiple object tracking (MOT) paradigm, in which subjects tracked 3–6 balls, to determine attentional capacity, and a change blindness paradigm similar to those used throughout VSTM literature, in which subjects had to remember 4, 6, or 8 objects, to determine VSTM capacity. We found that while the capacities are similar in some subjects, overall, there was weak to no correlation between the two. This finding is surprising given the amount of overlap seen between the two processes (Awh & Jonides, 2001; Awh et al, 2006; Downing, 2000; Todd et al, 2005). Our supposition is that there are certain underlying processes, such as target selection, encoding, and maintenance, and distractor suppression, that may be highly correlated between the two processes that that these underlying processes are driving the weak correlation we have seen, along with the overlap seen by others.
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