The melody of surprise: maternal surprise vocalizations during play with her infant

Two groups of mothers and their infants (24 infants, mean age = 3.5 months and 24 infants, mean age = 5.5 months) were video- and audio-taped in their homes while playing with a Jack-in-the-box. The mean fundamental frequency of spontaneous surprise exclamations of mothers when opening the toy were analysed, and infant and maternal facial expressions of surprise were coded in three regions of the face. A t-test established that significantly more of the older children in comparison with younger children showed surprise (t = -2.96, df = 46, p < 0.005, 2-tailed). Twenty-nine per cent of the younger infants, in comparison with 67% of the older children showed facial expressions of surprise. A t-test of maternal pitch height (Hz) indicated that mothers exclaimed in surprise with a higher pitch when the child did not show a surprise facial expression (mean = 415.61Hz) in comparison with the child showing surprise (mean = 358.97Hz; t = 2.9, df = 46, p = 0.006, 2-tailed). A multiple regression established that infant's expression was a stronger predictor of maternal vocal pitch than was the age of the infant. These results are discussed in terms of maternal use of emotional expressions as 'social signals'. Copyright (C) 2002 John Wiley Sons, Ltd.