Signal Clarity for Infant Quantity Representation

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Previous research has established that young infants discriminate large numerosities at a 1:2 ratio difference by 6 months, and sometimes show more precise comparison of small quantities (e.g. Cordes & Brannon, 2009a; Xu & Spelke, 2000); however, infants frequently fail in comparisons that cross the small and large number divide (e.g. 2 vs 4, 3 v 6). This failure has been attributed to a possible early dissociation between the systems engaged in small and large quantity processing. Here we provide new data that suggest that successful discrimination may depend on the clarity of the signal presented to the infant, which is a function of redundant stimulus dimensions (e.g. numerosity, surface area, and cumulative contour).

In two studies we tested 34 nine-month-old infants with comparisons that cross the small-large number divide and with surface area differences infants have previously failed to discriminate. Study 1 investigated infants’ discrimination of 2 versus 4 items with a 2 fold surface area change; Study 2 tested infants’ discrimination of 3 versus 4 with a 1.5 fold surface area change. Infants were presented with redundant correlated information across the habituation trials. Looking time measures comparing the last habituation trial to the first novel trial indicated successful discrimination, (Study 1, t(15)=3.12, p<.01; Study 2, t(17)=2.67, p=.02). These studies contribute to the limited body of research that has shown infant discrimination of differences at such small ratios (3:4) and across the small-large number divide, and support the hypothesis that increased signal clarity amplifies infants’ numerical discrimination.


Budapest Central European University Conference on Cognitive Development (BCCCD)


Budapest, HU