Poverty, problem behavior, and promise: differential susceptibility among infants reared in poverty.

Do infants reared in poverty exhibit certain physiological traits that make them susceptible to the positive and negative features of their caregiving environment? Guided by theories of differential susceptibility and biological sensitivity to context, we evaluated whether high baseline respiratory sinus arrhythmia (RSA) operates as a susceptibility factor among infants reared in poverty (N = 73). Baseline RSA at 5 months, the quality of the attachment relationship at 17 months, and the interaction of these two factors were included in our models as predictors of problem behavior at 17 months. Consistent with theory, results showed no significant differences in problem behavior among infants with low baseline RSA; however, infants with high baseline RSA exhibited the lowest levels of problem behavior if reared in an environment that fostered security, and they exhibited the highest levels of problem behavior if reared in an environment that fostered disorganization. These results have important implications for the psychological health of infants living in poverty.