Numerical Transformations in Five-month-old Human Infants

Abstract

We explore numerical abilities in five-month-old infants. Wynn (1992) showed that, when an object is added to or removed from a set of one or two hidden objects, fivemonth-old infants can infer the result of this transformation. However, in Wynn’s experiment, the objects were always placed at the same two locations. Hence, it remained an open question whether infants developed numerical or location-based expectations. To address this question, 56 five-month-old infants were tested using a violation of expectation paradigm with possible (1+1=2 or 2‐1=1) and impossible (1+1=1 or 2‐1=2) events. One group was tested in conditions identical to Wynn (1992). The other group saw objects being placed on a rotating tray. Since the locations of objects were not predictable, the development of non-numerical, location-based expectations was prevented. Infants in both groups looked longer at numerically impossible events than at the related possible events. These results suggest that infants use a more abstract representation than object location, the numerical nature of which is discussed. Recent experiments suggest that very young infants, and even newborns, are able to discriminate small sets of items according to their numerosity. Ten- and fourmonth-old infants have been shown to habituate to a set of two or three dots and to dishabituate when the numerosity changes from two to three or vice versa (Starkey & Cooper, 1980; Strauss & Curtis, 1981). Similar results have been obtained with numerosities of three versus four, but not when larger numerosities