Imitating seems easy, just smile when someone smiles at you, but is hard to explain. How can I make my action, which I feel but don’t see, similar to yours, which I see but don’t feel? Two types of opposing theories attempt to explain the mechanism underlying imitation: transformational and associative. Despite ample empirical behavioural and neurophysiological support for the associative theory, some key findings seem congruent with the transformational account and seem to contradict the associative account. As a result, the associative theory faces two challenges. Can the associative account explain imitation 1) when the agent seems to know her action is similar to the action of another person (similarity challenge), and 2) when there has been little or no opportunity for visuomotor learning (novelty challenge)? This project addresses the novelty and similarity challenges in four independent studies, involving infants and adults, with each study directly contrasting hypotheses derived from associative and transformational accounts of imitation. The project outcomes will not only help us to understand how imitation is accomplished, but will also provide novel insights into various other domains, such as language learning, development, social bonding, and action recognition, as each of these competences builds on imitative abilities.