Preliminary results from a twin study of infant--caregiver attachment

Two pilot studies were conducted. First, the validity of a measure of infant-caregiver attachment for twins was assessed. Sixteen twin pairs from the Louisville Twin Study (LTS) were assessed in the Strange Situation (SS) at ages 19 or 25 months. Concordance between the LTS procedure and the SS procedure for assessing attachment was 78.1%, significantly greater than chance. Second, twin similarity for attachment as measured by the LTS procedure was assessed. Videotapes of 34 MZ pairs and 26 DZ pairs at ages 18 and 24 months were rated in terms of attachment behavior. MZ concordance for attachment was 67.6%, significantly greater than the DZ concordance rate of 38.5%. Results are discussed in the context of current debate in attachment theory.