Robustness of individual identity in the cries of human infants.

This study investigated the possibility that one function of the human infant's cry is to convey individual identity across distance. Six-hundred adults, having been exposed to 30 s of an infant's crying, were asked to identify this infant on the basis of other, experimentally altered, cries. The cries were altered naturally by rerecording across distance in the out-of-doors, and artificially by bandpass filtering and temporal reorganization. The individuality of cries proved remarkably robust to degradation: Only when frequencies were limited to the range of 8 to 10 kHz was recognition performance significantly impaired. It is argued that the human infant's cry, a complex signal with multiple markers of individuality, may have among its functions the communication of infants' identities across distance.