The development of laughter in mother-infant communication: Timing parameters and temporal sequences

Laughter occurs in contexts of social interaction where coactive vocalizing is a common mode of exchange. This study looked at the timing parameters—mean duration of laugh, rate per minute of laughter and proportion of session laughed, and temporal sequence patterns—isolated, self-repetitive, reciprocal, and coactive in mothers and infants over the first 2 years. Timing parameters of infant laughter were found to stabilize by the end of the first year, but the timing of onset and offset times of coactive laughter between mother and infant became increasingly closer during the second year, and temporal sequence patterns were still changing in the second year. Most infant and maternal laughter was nondyadic and isolated, occurring more than 4 s after any previous laugh. In the second year, infants had a significantly greater proportion of self-repetitive laughter than mothers, and mothers had a significantly greater proportion of reciprocal laughter than infants. These findings are discussed in relation to multifunctional concepts of laughter and social dynamics of interaction.