An ethological analysis of human infant crying: answering Tinbergen's four questions.

The proximate causes, survival value, ontogeny, and evolutionary history of human infant crying are examined. Experiments and field observations involving infant distress vocalizations and begging calls in avian, mammalian, and nonhuman primate species are considered, as are ethnographic records of infant care and responses to crying in nonindustrialized societies. It is argued that human infant crying evolved as a primarily acoustic, graded signal, that it is a fairly reliable, if imperfect, indicator of need for parental care and that its primary function is to promote parental caregiving. Selection pressures that may have shaped the evolution of crying and its potential for corruption through dishonesty also are discussed. Copyright 2001 John Wiley & Sons, Inc.