Arithmetic Reasoning In Infancy

The studies described above suggest that infants may be able to discriminate the number of elements in a visual array or in a sequence of events. We now turn to the question of what types of operations infants' numerical representations might support. Do infants appreciate ordinal relationships between numerosities? Can infants add or subtract?

6.5.1 Ordering

Although previous work suggested that infants do not represent ordinal relationship between numerosities in the first year of life (Cooper, 1984; Strauss and Curtis, 1984), Brannon (2002a) recently found evidence that infants as young as 11 months old can make ordinal numerical judgments. In that study, infants were habituated to ascending or descending numerical sequences (see Figure 6.9). For example, infants habituated to the ascending ordinal direction were shown a small numerosity followed by a larger numerosity followed by an even larger numerosity. Between trials the absolute values changed but the ordinal direction was constant. Infants were then tested with new numerical values where the ordinal direction was maintained or reversed. Eleven-month-old infants looked for significantly longer when the ordinal direction was reversed.

In related work, Feigenson et al. (2002a) tested 10- and 12-month-old infants on their ability to choose the larger of two food quantities. The paradigm directly paralleled that used by Hauser et al. (2000) described above. The experimenters successively dropped graham crackers into each of two buckets and then allowed the infants to crawl to either bucket. Infants at both ages spontaneously chose the bucket with the larger number of crackers when tested with 1 vs. 2 and 2 vs. 3 comparisons, but not with 2 vs. 4, 3 vs. 4, and 3 vs. 6. These results suggest that the numerical ratio was not what controlled performance, but instead that infants were limited by the absolute set size of the values being compared. However, the infants also seemed to represent the absolute amount of food. When food amount was equated (e.g., one large and two small crackers), the infants chose randomly. This is not surprising given that the infants should be motivated to maximize food a) Example Habituation Trial a) Example Habituation Trial b) Example Familiar Test Trial b) Example Familiar Test Trial c) Example Novel Test Trial c) Example Novel Test Trial

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