Individual differences in 10-month-olds' performance on the A-not-B task.

This study used the classical A-not-B task (Piaget, ) to explore individual differences in cognitive flexibility in 10-month-old infants by: (1) examining how differences in search performance during A trials relate to search performance during B trials; (2) studying the relation between temperamental dimensions and A-not-B performance; and (3) investigating differences in search performance between looking and reaching responses within the same task. Forty infants were tested on a fixed-design-version of the A-not-B task, not allowing for training or individual adjustment, but instead eliciting additional search behaviors than the common correct responses in A trials and perseverative errors in B trials. Infants were also rated by their parents on the temperamental scales Activity level and Attention span. The main findings were: (1) performance on A trials affected B trial performance, with infants being more correct on A trials having more incorrect and less 'no search' responses on B trials; (2) activity level, but not attention span, was related to performance on the A-not-B task, with infants performing better on A trials having a lower activity level; and (3) there were a few differences in performance with regard to modality, indicating that responding correctly by looking may be less cognitively demanding than doing so by reaching. This study demonstrated that 10-month-olds show a wide variation of search behaviors on this A-not-B task, resulting in individual differences in performance. These differences are suggested to reflect variation in temperamental activity level as well as maturity of short term/working memory, inhibition and cognitive flexibility.