A variation of the social context in the warm-up period influences 18-month-olds’ imitation

The present study aimed to investigate how the prior social disposition of a model in a warm-up period influences 18-month-old infants’ subsequent imitation. Infants were randomly assigned to an interactive and social warm-up period (n = 19) or a non-interactive and non-social warm-up period (n = 19) with the model prior to the imitation task. They then participated in an imitation task with different types of actions: novel means actions, arbitrary vs. functional actions and necessary vs. unnecessary actions. An additional social warm-up control group (n = 14) and a non-social warm-up control group (n = 14) were recruited to assess the spontaneous production of the target actions in the absence of the demonstration. The results showed that infants in the experimental groups performed significantly more target actions than infants in the control groups, showing an imitation effect. Furthermore, the results of the experimental groups showed that the overall imitation performance of the target actions was higher in the social condition than in the non-social condition. This imitation enhancing effect of the social warm-up period held true for the novel means actions and functional vs. arbitrary actions, however not for the necessary vs. unnecessary actions. Implications of the results for theory and future studies are discussed in terms of infants’ social motivation and its relation to infants’ imitative behavior