Background: Scholars acknowledge that both biologically-founded child temperament and environmental factors are influential in determining the quality of infant-mother attachment. We present evidence for gene by environment (G x E) interaction in the organization of attachment.
Methods: Participants were 88 typically developing infants and their mothers. Molecular genetic measures of the infants focused on the polymorphism in the serotonin transporter gene (5-HTTLPR, ss/sl vs. ll genotype). Mothers' responsiveness to their infants at 7 months was observed in lengthy naturalistic interactions, and was conceptualized as the environmental influence.
Results: For infants with a short allele (ss/sl ), variation in mothers' responsiveness was significantly associated with attachment security, assessed at 15 months in the Strange Situation. For those infants, low responsiveness predicted particularly high risk for insecure attachment, and high responsiveness offset that risk. For infants homozygous for the long allele (ll ), there was no association between responsiveness and attachment organization.
Conclusions: The findings show that the quality of early care serves to amplify or offset the risk conferred by genotype.