Individual differences in the human infant cry in a comparative perspective [abstract]

Francesca Rocca, Daniela Lenti Boero & Carlo Lenti (2002). Individual differences in the human infant cry in a comparative perspective [abstract]. Bioacoustics, Volume 13 (2): 195

Animal studies indicate that many primate species recognise the individual characteristics of sounds of both adult and young. In human newborns, the successful individual perceptive attribution of the cries by the adult care-giver indicate that it may be considered an "acoustic signature'' (Green & Gustafson 1983: Developmental Psychobiology, 16, 485-493). In this study we attempted to find whether some sound parameters are better than others in individual discrimination. We recorded 64 cries induced by cynetic stimulation from 32 infants in their first and second day of life successively, and preliminarily analysed 11 parameters from 1628 wails. In phonated cries (i.e. wails with clear fundamental frequency) we found that 17 (53%) infants did not significantly change more than two parameters in the two successive recordings. A discriminant function analysis performed with SPSS software showed that 62% of the cries could be correctly discriminated on the base of sex (F5,759 = 7.91, P < 0.000). Twenty-two (69%) infants, subdivided in six smaller groups, could be individually discriminated. However, only 53% of the cries could be correctly assigned to an individual infant. Consequently, infants varied greatly in discriminability: from 97% of the cries to 0%. In individual discrimination, none of the sound parameters was privileged in entering the discriminant function. As regards individual discriminability, the number of cries from an infant was the only significant parameter for successful discrimination (F1,30 = 28.07, P < 0.000). Results are discussed within a comparative frame of hominid maternal care evolution and sound comparison with other primate species.