Graded motor responses in the time course of categorizing atypical exemplars.

The time course of categorization was investigated in four experiments, which revealed graded competitive effects in a categorization task. Participants clicked one of two categories (e.g., mammal or fish) in response to atypical or typical exemplars (e.g., whale or cat) in the form of words (Experiments 1 and 2) or pictures (Experiments 3 and 4). Streaming x, y coordinates of mouse movement trajectories were recorded. Normalized mean trajectories revealed a graded competitive process: Atypical exemplars produced trajectories with greater curvature toward the competing category than did typical exemplars. The experiments contribute to recent examination of the time course of categorization and carry implications for theories of representation in cognitive science.