Infants' Use of Force to Defend Toys: The Origins of Instrumental Aggression.

The two aims of the study were (a) to determine when infants begin to use force intentionally to defend objects to which they might have a claim and (b) to examine the relationship between toddlers' instrumental use of force and their tendencies to make possession claims. Infants' and toddlers' reactions to peers' attempts to take their toys were assessed in three independent data sets in which the same observational coding system had been used (N = 200). To ensure that infants' use of force was goal-directed and not a simple physical reaction, we recorded infants' reactions when peers picked up toys that the focal infants had just put down, or were nearby or in the focal infants' mothers' laps. The use of force in response to peers' taking over toys was evident before the first birthday, but more common thereafter, although only a minority of children in each sample used force. Analysis of a combined data set revealed that force was deployed more often by 2-year-olds than younger infants, and was significantly associated with verbal references to people's possession of objects. These observations show that toddlers do deploy force intentionally to defend their possessions.