Performed a strange situation study to investigate confusions over the relative importance of parent-infant interaction and individual temperament to the formation of attachment relationships, as well as conflicting data over similarity of attachment between parents and infants. They found that infant-mother attachment was independent of infant-father attachment.

They classified infants by degree of distress (A1-B2 vs. B3-C2) and found this resulted in significant similarities between the relationship with both parents, autonomic stability and orientation as a newborn, and 3-month assessment of temperament by mothers. None of these factors showed significant relationships when other classifications (anxious/ambivalent, secure, avoidant or secure, insecure) were used. They concluded that “temperament affects not so much whether or not an infant will develop a secure attachment relationship with his or her mother as rather the manner in which security or insecurity may be expressed under the conditions of the Strange Situation experiment.” (p. 793).