The 36 month parent–infant interactions were coded using the Iowa Family Interaction Rating Scales (Melby, Conger, Book, Rueter, & Lucy, 1998), a global rating system designed to measure the behavioral characteristics of individual parents and children and the quality of behavioral exchanges directed from parent to child and vice versa. The rating scales are designed to measure both verbal and non-verbal behaviors as well as affective aspects of the interaction. The warmth/sensitivity composite at 36 months included items such as positive reinforcement, sensitive child centered behaviors, humor, positive mood, warmth-support, prosocial behaviors, and physical affection. The internal consistency (Cronbach's alpha) for these composite scales was .89 for both mothers and fathers.
