Signal Clarity for Infant Numerical Representation
Previous research has established that young infants represent and discriminate large numerosities approximately and do so in ways that appear limited by the ratio differences between quantities (e.g., Cordes & Brannon, 2009a; Xu & Spelke, 2000). That is, infants at 6 and 9 months have shown successful discrimination of numerosities that differ by a 2:3 ratio (Cordes & Brannon, 2009; Xu & Arriaga, 2007) but have failed in smaller ratio comparisons (e.g., 3:4 and 4:5, Feigenson, Carey, & Hauser, 2002; Xu & Arriaga, 2007). We hypothesize, however, that successful discrimination depends on the clarity of the signal presented to the infant. We suggest that signal clarity is a function of 1) the statistical regularities that come from the presentation of redundant and correlated stimulus information, as well as 2) certain visual properties, such as density of items that make numerical information easier or more difficult to extract. In Study 1 we tested 20 nine-month-old infants in a 3:4 ratio comparison in which they were presented redundant correlated information across the habituation trials. Whereas previous studies indicated failure when dimensions were not redundant, looking time measures in our study comparing the last habituation trial to the first novel trial indicated successful discrimination, t(19)=2.56, p=.019. In Study 2 we tested 66 six-month olds in a 2 v 3 visual comparison—a comparison in which infants have previously succeeded (e.g., Antell & Keating, 1983; Starkey & Cooper, 1980). In this study infants successfully discriminated the sets when items were spaced far apart at a low density (looking time to novel versus familiar, t(31)=2.81, p<.01); however, infants failed when items were closely spaced at a high density, t(33)=1.60, p=.14. The results suggest that both redundancy of visual information as well as item density contribute to signal clarity and influence representation and discrimination of numerical stimuli.
Vision Sciences Society Annual Meeting (VSS)
Cantrell, Lisa, Ty W. Boyer, Lisa Smith.
"Signal Clarity for Infant Numerical Representation."
Psychology Faculty Presentations.