Longitudinal evidence that infants develop their imitation abilities by being imitated.

Humans are widely considered the most socially sophisticated species on the planet. Their remarkable abilities in navigating the social world have given rise to complex societies and the advancement of cultural intelligence. But what characterizes us as ultra-social beings? Theoretical advances in social sciences over the last century purport imitation as a central mechanism for the emergence of humans' unique social-cognitive abilities. Uncovering the ontogeny of imitation is therefore paramount for understanding human cultural evolution. Yet how humans become able to imitate is unclear and intensely debated. Recently, multidisciplinary findings have challenged long-standing assumptions that imitation is inborn. So what are the underlying processes supporting the development of imitation? One fascinating possibility is that infants become able to imitate by being imitated. Cognitive theories have suggested that by perceiving others imitating one's own behavior, visual and motor representations of that behavior are coactivated and associated, leading to the emergence of imitation abilities. Here, we show that being imitated by sensitive caregivers in infancy constitutes a psychological process giving rise to infants' imitation abilities. Results demonstrated (1) that maternal imitation at 14 months positively predicted infants' imitation abilities at 18 months and (2) that maternal imitation at 14 months mediated the positive effect of maternal sensitivity at 6 months on infants' imitation abilities at 18 months. This offers substantial evidence for the role of social interactions in the emergence of imitation as a key factor for human cultural learning.