Fig. 1.

Description of Why/How Task. Following a fixation cross presented for an average of 9 s, each of the 16 experimental blocks began with a prompt question shown for 2.1 s followed by a blank screen lasting 0.15 s before presenting a sequence of eight trial images. Participants were given a max of 2.2 s to respond to each image, and a reminder prompt lasting 0.3 s was shown between each image. Each pre-block prompt began with ‘Is the person’ followed by a descriptive phrase specific to each question. This same phrase was then shown as a reminder between each trial. Recorded BOLD signal was analyzed in a variable epoch manner beginning from the onset of the first image to the offset of the final image of the block. The Why prompts described either intentions inferred from a person's bodily actions (e.g. ‘helping someone’) or emotional states inferred from facial expressions (e.g. ‘proud of themselves’). The How prompts described the physical mechanics of body actions (e.g. ‘lifting something’) or facial orientations (e.g. ‘opening their mouth’). The same set of images were used for both Why and How trials, and participants responded ‘yes’ or ‘no’ with their index or middle finger to indicate whether the person(s) in each image demonstrated that mental state or were performing the action stated in the prompt. On average, the task lasted approximately 4.9 min per person. See online Supplemental Information for additional prompt examples and task information.