Response modality affects human infant delayed-response performance.

Delayed response performance was assessed in 120 7-, 9-, and 11-month-old infants with correct response defined as either retrieval of a hidden object or gaze toward the location where the object was hidden. Performance improved with age, was above chance for each age group in each condition, and was more often correct with the gaze response. When direction of gaze and reach differed, direction of gaze was more likely to be correct. Infants in the reach condition were more likely to fail to reverse a previously correct response (i.e., to make the A-not-B error). Perseverative responding occurred frequently and was more likely in the reach than the gaze condition. This effect emerged primarily in the context of an incorrect response, which suggests modality-specific sensitivity to the effect of priming rather than reinforcement. Many infants showed strong side biases, and there was a tendency for more reaches to the left but gazes to the right. In a second experiment, 12 5-month-olds gazed toward the correct location more frequently than would be expected by chance but failed to reverse a previously correct response more often than older infants. These findings indicate that response modality has a significant effect on delayed-response performance.