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Jennifer Zosh, Lisa Feigenson; Developmental evidence for a capacity-resolution tradeoff in working memory. Journal of Vision 2010;10(7):727. doi: 10.1167/10.7.727.
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A recent debate in the study of visual short-term memory (VSTM) asks whether capacity is better characterized as limited by the number of items stored (Luck & Vogel, 1997), the total information load of the items (Alvarez & Cavanagh, 2004; Xu & Chun 2006), or by a hybrid of these (Gao, Li, Liang, Chen, Yin & Shen, 2009; Zhang & Luck, 2008). Here we extend the scope of this capacity-resolution debate by studying infants and by using a working memory rather than a VSTM task. We asked whether the resolution of infants' object representations decreases as infants remember larger numbers of objects. We presented 18-month-olds with arrays of 1-3 toys that were then hidden in a box. Infants were allowed to search for and retrieve all of the hidden objects, and we measured their subsequent searching. On some trials infants retrieved exactly those objects they saw hidden (e.g., brush and car hidden; brush and car retrieved), and as a result then searched very little (because the box was expected empty). On other trials, one or more of the retrieved objects secretly switched identity (e.g., brush and car hidden; duck and car retrieved). On these trials the number of retrieved objects was always correct, but if infants remembered the identity of the initially hidden objects they should detect a mis-match and continue searching for the missing objects. In three experiments we found that infants' ability to detect this kind of identity switch decreased as the number of hidden objects increased. These studies expand the capacity-resolution debate in two ways: First, they provide evidence of a tradeoff in infants, suggesting that capacity and resolution interact from early in the lifespan. Second, they extend existing results to a longer timescale, suggesting that capacity and resolution trade off beyond VSTM, in memory more broadly.
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