Semantic Similarity of Social Functional Smiles and Laughter

Laughter and smiles co-occur and accomplish similar communicative tasks. Certain smiles and laughter elicit positive affect in the sender and the recipient, serving as social rewards. Other smiles and laughter lack this positivity but retain a message of harmlessness and affiliation that lubricates the interaction. And finally, some smiles and laughter convey disapproval or dominance in a less serious way than more overt displays (e.g., frowns). But work on the social functions of smiles and laughter has progressed independently. We ask whether smiles and laughter are judged as more alike if they are high on the same social functional dimensions. First, online participants’ ( N = 244) judged the similarity of a set of validated reward, affiliation, and dominance smiles to each other, resulting in a 2-dimensional semantic smile space. Then we inserted laughter clips (rated on the social functional dimensions in prior work) into the semantic smile space using new participants’ ( N = 1089) responses on a smile-laughter similarity task. The laugh samples grouped in the smile space according to their previously determined social function, suggesting participants’ judgments about smile-laughter similarity were partly guided by the reward, affiliation, and dominance values of the displays. Trial-level analyses indicate reward and affiliation smiles were most likely to be matched to reward and affiliation laughs, respectively, but dominance displays were more complicated. This suggests perceivers judge the meaning of smiles and laughs along reward, affiliation, and dominance dimensions even without verbal prompts. It also deepens our understanding of the functional overlap of smiles and laughter.