Fig. 1.

(A) Logic of experiment 1. The experiment consists of four unmorphed adaptor actions (green squares), and two morph axes from which test stimuli were sampled. Each axis morphed between two actions: throwing and giving (Left red square); and catching and taking (Right red square). Experiment 1 combined adaptors and morph axes in different ways. Under normal adaptation conditions, the test stimuli were generated by morphing between the adapted actions (solid arrows). In the cross-adaptation condition, the test stimuli were generated from the other two adaptor actions that were not used during adaptation (dotted lines). (B) Schematic outline of a single experimental trial: four adaptor repetitions preceded the ambiguous test stimulus presentation. Depending on the condition, the participants’ task was to indicate, for example, whether the test stimulus looked more like a give or a throw action (see Methods for details).