Triangles have goals too: Understanding action representation in left aIPS

Humans freely interpret moving shapes as being “alive” and having social intentions, such as beliefs and desires. The brain systems underpinning these processes are the same as those used to detect animacy and infer mental states from human behaviour. However, it is not yet known if the brain systems that respond to human action-goals also respond to the action-goals of shapes. In the present paper, we used a repetition suppression paradigm during functional magnetic resonance imaging (fMRI) to examine brain systems that respond to the action-goals of shapes. Participants watched video clips of simple, geometrical shapes performing different ‘take-object’ goals. Repeated presentation of the same goal suppressed the blood oxygen level-dependent (BOLD) response in left anterior intraparietal sulcus (aIPS), a brain region known to distinguish the goals of human hand actions. This finding shows that left aIPS shows similar sensitivity to the action-goals of human and non-human agents. Our data complement previous work on animacy perception and mental state inference, which suggest components of the social brain are driven by the type of action comprehension that is engaged rather than by the form of the acting agent (i.e., human or shape). Further, the results have consequence for theories of goal understanding in situations without access to biological form or motion.