CRYING IN IKUNG INFANTS: A TEST OF THE CULTURAL SPECIFICITY HYPOTHESIS

Despite infant care practices differing markedly from the authors' own, the similar pattern of infant cry/fret behaviour in !Kung infants implies that this pattern is not specific to industrialized societies, suggesting the early crying peak may represent a behavioural universal characteristic of the species.

Abstract

The crying of normal and “colicky” infants increases in duration until six weeks of age and declines to baseline by four months. To determine whether this pattern is specific to infant care practices typical of Western industrialized societies, cry and fret behaviour was analyzed in infants of the !Kung San, a hunter-gatherer society whose infant care includes continuous carrying and feeding, upright posture, and maternal responsivity--all of which affect crying behaviour. Six 15-minute timed 5-second interval observations were carried out at 68 age points on 33 infants between one and 99 weeks of age. Frequency and total duration of cry/fret episodes per waking hour estimated for each age point were assigned to one of 7 age periods. Cry/fret duration (min/hr) varied significantly with age (ANOVA F=3.85;df 6,61; p<0.002) with the peak at 3 months (4.5 min/hr) returning to baseline by 5 months (1.7 min/hr). The patterns were similar and significant when cry duration (F=2.47; df 6,61;p=.03) and fret duration (F=3.47;df 6,61;p=.002) were considered separately. Frequency of cry/fret episodes showed the same pattern (3 month peak = 20/hr; 5 month baseline = 12/hr) but was not significant (F=1.5;df 6,61;p=0.19). Conclusion: Despite infant care practices differing markedly from our own, the similar pattern of infant cry/fret behaviour in !Kung infants implies that this pattern is not specific to industrialized societies. The early crying peak may represent a behavioural universal characteristic of the species.