Investigated infant preferences for interaction with mother vs father, similarities and differences in maternal and paternal behavior, and the influence of a 2nd parent's presence on parent-infant interaction. 40 middle-class families with 15-mo-old infants were observed in their own homes on 2 separate weekdays, for 2 hrs/day. Analysis revealed more similarities than differences in maternal and paternal behavior, limited preferences for interaction with same-sex children, and more active parenting when alone with the child than when in the presence of the spouse. Infant behavior was similarly influenced by social situation, with more social behavior directed toward each parent when alone with them. Finally, covariance analysis revealed that displayed general preferences for interaction with father were primarily a function of parental behavior. (18 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.