The affordance-matching hypothesis: how objects guide action understanding and prediction

Abstract

Action understanding lies at the heart of social interaction. Prior research has often conceptualized this capacity in terms of a motoric matching of observed actions to an action in one's motor repertoire, but has ignored the role of object information. In this manuscript, we set out an alternative conception of intention understanding, which places the role of objects as central to our observation and comprehension of the actions of others. We outline the current understanding of the interconnectedness of action and object knowledge, demonstrating how both rely heavily on the other. We then propose a novel framework, the affordance-matching hypothesis, which incorporates these findings into a simple model of action understanding, in which object knowledge-what an object is for and how it is used-can inform and constrain both action interpretation and prediction. We will review recent empirical evidence that supports such an object-based view of action understanding and we relate the affordance matching hypothesis to recent proposals that have re-conceptualized the role of mirror neurons in action understanding.

Keywords: action prediction; action understanding; affordances; object function; object manipulation.

Figure 1

Affordance matching during action observation. Top panel: object identification provides information about what an object is for (function knowledge) and how it has to be manipulated to realize this function (manipulation knowledge). Middle panel: flow of information during action prediction. Inferred goals of an actor activates objects with matching functions. The associated manipulation knowledge predicts forthcoming movements. Bottom panel: flow of information during action interpretation. Observed behavior that matches an object’s manipulation activates the corresponding function, which in turn provides information about the actor’s goal.

Figure 2

Concrete example for the flow of information during action prediction and interpretation. Top panel: Action prediction. Prior knowledge of an actor’s goal (shooting) activates knowledge of objects with corresponding function. The associated manipulation knowledge (raising the arm, pulling the trigger) supports action prediction by biasing visual perception towards these manipulations. Lower panel: Action interpretation. Observed behavior is matched to the manipulations supported by the object. If both match, the corresponding functions are activated, providing likely goals of the actor.