Dutch and Japanese listeners' perception of group membership from spontaneous and volitional laughter

The 16 laughter stimuli were presented to participants via headphones from a computer. On each trial, participants heard a laugh and were asked in a two-way forced-choice task 1) whether the laugh was spontaneous, which happens when someone finds something really funny (e.g., a hilarious joke) or volitional, which happens when someone is laughing to be nice even though they do not think something is funny (e.g., a joke that is not funny at all), and 2) whether the laughing person was from their own or cultural group or foreign. Participants also rated the positivity of each clip on a 7-point Likert scale ranging from 1 (“A little positive”) to 7 (“Very positive”). The scale was presented with accompanying smiley faces (see Supplementary Materials Figure S1). The presentation order of the stimuli and questions was randomised separately for each participant. They could replay each stimulus as many times as they wanted.