Crying

The Function of Crying in Infancy

Crying is one of several reflexive behaviors present at birth that serve to promote proximity to a caregiver. Many mammals—species with mammary glands to nurse young—cry or call when separated from a caregiver, and crying typically prompts reunion with a mother or caregiver. Human infants, like other mammals, cry when they are separated from their caregivers, and for the most part, they stop crying when picked up or held. Crying is therefore believed to be an attachment behavior with conservative evolutionary history, rooted in infants’ need for adult care.

Two aspects of crying, however, appear to be uniquely human. Only human infants cry in the presence of an attentive caregiver (as in the case of colic, a syndrome characterized by excessive, inconsolable crying in early infancy), and only humans shed emotional tears (i.e., tears triggered by emotion rather than irritation of the eyes).

Although infant crying is widely seen as an adaptive, species-typical behavior designed by evolution to elicit care, crying is also associated with negative outcomes. Crying is the most frequent complaint brought to pediatricians by parents of young infants, and it is the most frequently cited trigger of infant abuse. The irritating nature of the crying sound is likely behind its effectiveness in mobilizing caregivers to perform actions that arrest crying.

The fact that crying is difficult to tolerate, however, may place some infants at risk for abuse if an adult exposed to crying is not motivated to provide care or if crying is inconsolable. Some have argued that the amount of crying typical of modern, industrialized societies is out of sync with human evolutionary history and could be provoking neglectful or abusive responses.

Because infant crying is primarily an auditory signal, the acoustic parameters of infant cries have been well described. In addition to alerting caregivers that an infant needs attention, the sound of crying conveys information about an infant’s health. Cri-du-chat, a genetic disorder also known as 5p deletion syndrome, is named for the unusually high-pitched cries of affected infants. Atypical infant cries characterize numerous other genetic disorders, infectious diseases, and environmental insults, including premature birth, bacterial meningitis, Down syndrome, and most recently, autism. Crying may have functioned in the course of human evolution to guide parental decisions about whether to invest in or abandon offspring. In modern times, infant crying is a potentially useful clinical sign aiding in the diagnosis of childhood disease.

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