Humour and laughter are universal to the human psychological experience and have serious developmental and evolutionary implications. Despite the early emergence of laughter in infancy, infants have been largely ignored in the humour research and humour has been largely ignored in the infant research. The present study describes the emergence of humour perception and creation in a sample of 20 parent–infant dyads who were followed from ages 3‐to‐ 6 months. The study examined how infants discover that absurd nonverbal behaviour, known as ‘clowning’, is amusing in the context of social engagement with caregivers. Results indicate that parents primarily use clowning when attempting to amuse their infants and pair these behavioural absurdities with affective cues like smiling and laughing. As they got older, infants were more likely to laugh and smile in response to clowning. Infants' ability to create humor via clowning also increased with age, starting with simple shrieks at 3 months to imitating absurd actions by 5 months. These increases are partly potentially explained by accompanying increases in parental smiling, laughing and clowning in response to infant clowning. Future research should employ more diverse samples and experimentally investigate the role of parental affect and social referencing in infants' interpretation of absurd behavior. Copyright © 2011 John Wiley & Sons, Ltd.

Infancy is a critical time for the development of secure attachment, which is facilitated by emotionally synchronous interactions with parents. Humor development, which includes shared laughter and joint attention to an event, emerges concurrently with attachment, but little is known regarding the relationship, if any, between humor development and attachment in the first year. Thirty 3-month-old infants were videoed at home each month until they were 6-months old while their parents attempted to amuse them. Frequency of infants’ smiles and laughs served as a measure of “state humor”, and the smiling/laughing subscale of the Infant Behavior Questionnaire-Revised served as a measure of “trait humor”. State and trait humor were not correlated. Lower trait humor as 6 months predicted higher attachment security on the Attachment Q-sort at 12-months (r=. 46), suggesting that less good-humored infants elicit greater parental engagement, which works to the benefit of attachment, or vice versa. Future studies should examine the importance of smiling and laughter as they relate to other developmental phenomena in the first year.