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Abstract

Action recognition research has mainly focused on investigating the perceptual processes in the recognition of isolated actions from biological motion patterns. Surprisingly little is known about the cognitive representation underlying action recognition. A fundamental
question concerns whether actions are represented
independently or interdependently. Here we examined, whether
cognitive representation of static (action image) and dynamic (action movie) actions are dependent on each other and whether cognitive representations for static and dynamic actions overlap. Adaptation paradigms are an elegant way to examine the presence of relationship between different cognitive representations. In an adaptation experiment, participants view a stimulus, the adaptor, for a
prolonged amount of time and afterwards report their perception of a second, ambiguous test stimulus. Typically, the perception of the second stimulus will be biased away from the adaptor stimulus. The presence of an antagonistic perceptual bias (adaptation effect) is often taken as evidence for the interdependency of the cognitive representation between test and adaptor stimulus. We manipulated the dynamic content (dynamic vs. static) of the
test and adaptor stimulus independently. The ambiguous test stimulus was created by a weighted linear morph between the spatial positions of the two adapting actions (hand shake, high five). 30 participants categorized the ambiguous dynamic or static action stimuli after being adapted to dynamic or static actions. Afterwards, we calculated the
perceptual bias for each participant by fitting a psychometric function to the data. We found an action-adaptation after-effect in some but not all experimental conditions. Specifically, the effect was only present
if the presentation of the adaptor and the test stimulus was congruent, i.e. if both were presented in either a dynamic or a static manner (p\0.001). This action-adaptation after-effect indicates a dependency between cognitive representations when adaptor and test
stimuli have the same dynamic content (i.e. both static or dynamic). Future studies are needed to relate those results to other findings in the field of action recognition and to incorporate a neurophysiological perspective.