Social, cognitive, and physiological aspects of humour perception from 4 to 8 months: Two longitudinal studies.

Infants laugh by 4 months, but whether they understand humour based on social or cognitive factors is unclear. We conducted two longitudinal studies of 4-, 6-, and 8-month-olds (N = 60), and 5-, 6-, and 7-month-olds (N = 53) to pinpoint the onset of independent humour perception and determine when social and cognitive factors are most salient. Infants were shown six events in randomized repeated-measures designs: two ordinary events and two absurd iterations of those events, with parents' affect manipulated (laugh or neutral) during the latter. Four-month-olds did not smile/laugh more at absurd events, but exhibited a significant heart rate deceleration. Five-month-olds independently appraised absurd events as humorous, smiling/laughing despite their parents' neutrality. Parent laughter did not influence infants of any age to smile more, but captured 4-month-olds' attention. Results suggest that 4-month-olds laugh in response to social cues, while 5-month-olds' can laugh in response to cognitive features. Statement of contribution What is already known on this subject? By 6 months, infants can independently appraise absurd events as humorous, but it is not known whether younger infants can. What does this study add? This study replicated the finding on younger infants, showing that 5-month-olds are similarly capable of independent humour appraisal. These studies also found that although 4-month-olds do not respond to absurd events with positive affect, they do exhibit a heart rate decrease that is unrelated to looking. These studies help delineate when social and cognitive factors contribute to infant humour perception.

Laughing matters: Infant humor in the context of parental affect.

Smiling and laughing appear very early during the first year of life, but little is known about how infants come to appraise a stimulus as humorous. This short-term longitudinal study explored infant humor perception from 5 to 7 months of age as a function of parental affect during an absurd event. Using a within-participants design, parents alternated smiling/laughing with emotional neutrality while acting absurdly toward their infants. Group comparisons showed that infants (N = 37) at all ages smiled at the event regardless of parental affect but did so significantly longer at 5 and 6 months, and more often and sooner at 7 months, when parents provided humor cues. Similarly, sequential analyses revealed that after gazing at the event, 7-month-olds were more likely to smile at it only when parents provided humor cues and were comparatively more likely to look away when parents were neutral. Thus, starting at 5 months of age, parental affect influenced infants' affect toward an absurd event, an effect that was magnified at 7 months. These results are discussed in the context of emotional contagion, regulation, and the emergence of social referencing.