In this work I investigate the mechanisms that allow people to generate predictions about the actions of other people. For example, when engaged in certain joint tasks, such as playing a piano duet, it is necessary for the two actors to synchronise the execution of their actions. To do this, it is necessary for actors to be able to anticipate the actions of their co-actors. I have used behavioural experiments to investigate the possibility that during joint action actors use their action systems “off-line” in order to run simulations of their co-actor’s actions, and then use these simulations as the basis for anticipatory action planning. (Recent collaborators: John Sutton, Bill Thompson, Natalie Sebanz, Günther Knoblich)