Moving beyond discrete categories in motor cognition.

Theories on human action control assume the human mind copes with the computational challenge of selecting and performing goal-directed movements by recycling previous action plans. Feature binding assists this recycling by integrating stimulus and response features into episodic representations. Perhaps surprisingly, however, previous evidence for binding and retrieval is confined to categorical perceptual and motor features that define coarse-grained decisions. Here we show that such episodic representations can also incorporate continuous, metric information. These conclusions emerge from two experiments in which participants performed whole-arm pointing movements to varying target locations with their left or right hand. Short inter-trial distances between successive locations benefitted response repetitions (i.e., responding with the same hand in consecutive trials) whereas increasing distances benefitted response changes. This effect emerged as a direct function of metric distance. Feature binding and retrieval thus seem to go beyond categorical decision making, either by including metric information about current stimulation or by providing direct access to an agent's motor repertoire.