Mutuality Relations,Observation, and Intentional Constraints

This commentary focuses on the implications of Stoffregen's (target article, this issue) theory, as they apply to current research on human biological motion. We take up his suggestion that affordances, not events, are perceived and that data generated within event-perception research may reflect conversion of affordance-based perception to "event-based scales." Research on point-light walkers has been classed with event perception; however, results from our current research on perception of point-light sports displays suggest that accurate detection of humans and their actions in these displays may be controlled by complex relations better explained within an affordance-based account. We report the results of an experiment that controlled the presence and absence of relations between biological motion and a discrete environmental object. Detection was best when these affordance-relevant relations were available. Finally, we consider the utility of Stoffregen's ontological distinction as it may inform our understanding of past, current, and future research on perception of point-light walker displays.