Identifying others' informative intentions from movement kinematics.

Previous research has demonstrated that people can reliably distinguish between actions with different instrumental intentions on the basis of the kinematic signatures of these actions (Cavallo, Koul, Ansuini, Capozzi, & Becchio, 2016). It has also been demonstrated that different informative intentions result in distinct action kinematics (McEllin, Knoblich, & Sebanz, 2017). However, it is unknown whether people can discriminate between instrumental actions and actions performed with an informative intention, and between actions performed with different informative intentions, on the basis of kinematic cues produced in these actions. We addressed these questions using a visual discrimination paradigm in which participants were presented with point light animations of an actor playing a virtual xylophone. We systematically manipulated and amplified kinematic parameters that have been shown to reflect different informative intentions. We found that participants reliably used both spatial and temporal cues in order to discriminate between instrumental actions and actions performed with an informative intention, and between actions performed with different informative intentions. Our findings indicate that the informative cues produced in joint action and teaching go beyond serving a general informative purpose and can be used to infer specific informative intentions.