1 Cardiff University Centre for Human Developmental Science, School of Psychology, Cardiff University, Cardiff, UK. paineal@cardiff.ac.uk.
2 Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
3 School of Psychology, University of Sussex, Brighton, UK.
4 Faculty of Management, Law & Social Sciences, University of Bradford, Bradford, UK.
5 Department of Education, Concordia University, Montreal, Canada.

Humour plays a crucial role in children's early interactions, likely promoting the development of social understanding and fostering positive social relationships. To date, the connection between humour production in peer play and the development of social understanding skills in middle childhood has received limited attention. In a community sample of 130 children residing in the UK (M = 6.16 years old, range 5-7; 67 [51.5%] girls, 62 [47.7%] boys, and 1 [0.8%] non-binary child; 95 [73.1%] mothers and 85 [65.4%] fathers identified as Welsh, English, Scottish, or Irish), we tested our prediction that children's use of humour in play with peers would be positively associated with children's ability to understand the minds of others. We conducted detailed observational coding of children's humour production during peer play and examined associations with children's performance on a battery of social understanding assessments. Multilevel models showed that 42.8% of the variance in children's humour production was explained by play partner effects. When controlling for the effect of play partner and other individual child characteristics (age, gender, receptive vocabulary) children's spontaneous attributions of mental states were associated with humour production. Results are discussed considering how these playful exchanges reflect and influence the development of children's socio-cognitive competencies.