Behavioral and neural representations en route to intuitive action understanding.

When we observe another person's actions, we process many kinds of information - from how their body moves to the intention behind their movements. What kinds of information underlie our intuitive understanding about how similar actions are to each other? To address this question, we measured the intuitive similarities among a large set of everyday action videos using multi-arrangement experiments, then used a modeling approach to predict this intuitive similarity space along three hypothesized properties. We found that similarity in the actors' inferred goals predicted the intuitive similarity judgments the best, followed by similarity in the actors' movements, with little contribution from the videos' visual appearance. In opportunistic fMRI analyses assessing brain-behavior correlations, we found suggestive evidence for an action processing hierarchy, in which these three kinds of action similarities are reflected in the structure of brain responses along a posterior-to-anterior gradient on the lateral surface of the visual cortex. Altogether, this work joins existing literature suggesting that humans are naturally tuned to process others' intentions, and that the visuo-motor cortex computes the perceptual precursors of the higher-level representations over which intuitive action perception operates.