Keltner, D., & Bonanno, G. A. (1997). A study of laughter and dissociation: distinct correlates of laughter and smiling during bereavement.

aughter facilitates the adaptive response to stress by increasing the psychological distance from distress and by enhancing social relations. To test these hypotheses, the authors related measures of bereaved adults’ laughter and smiling 6 months postloss to measures of their (a) subjective emotion and dissociation from distress, (b) social relations, and (c) responses they evoked in others. Duchenne laughter, which involves orbicularis oculi muscle action, related to self-reports of reduced anger and increased enjoyment, the dissociation of distress, better social relations, and positive responses from strangers, whereas non-Duchenne laughter did not. Lending credence to speculations in the ethological literature, Duchenne laughter correlated with different intrapersonal and interpersonal responses than Duchenne smiles. Discussion focuses on the relevance of these findings to theories of positive emotion.

Keltner, D., & Bonanno, G. A. (1997). A study of laughter and dissociation: distinct correlates of laughter and smiling during bereavement. Journal of personality and social psychology, 73(4), 687-702.