Emerging self‐exploration by 2‐month‐old infants

Two‐month‐olds and newborns were tested in a situation where they had the opportunity to experience different auditory consequences of their own oral activity on a dummy pacifier. Modulation of oral activity was scored and analyzed relative to two types of contingent auditory feedback, either analog or non‐analog to the effort exerted by the infant on the pacifier. The dummy pacifier was connected to an air pressure transducer for recording of oral action. In two different experimental conditions, each time the infant sucked above a certain pressure threshold they heard a perfectly contingent sound of varying pitch. In one condition, the pitch variation was analog to the pressure applied by the infant on the pacifier (analog condition). In another, the pitch variation was random (non‐analog condition). As rationale, a differential modulation of oral activity in these two conditions was construed as indexing some voluntary control and the sense of a causal link between sucking and its auditory consequences, beyond mere temporal contingency detection and response–stimulus association. Results indicated that 2‐month‐olds showed clear signs of modulation of their oral activity on the pacifier as a function of analog versus non‐analog condition. In contrast, newborns did not show any signs of such modulation either between experimental conditions (analog versus non‐analog contingent sounds) or between baseline (no contingent sounds condition) and experimental conditions. These observations are interpreted as evidence of self‐exploration and the emergence of a sense of self‐agency by 2 months of age.