This study examines the developmental status of young mothers' social and logical-physical reasoning in relation to the characteristics of their interactions with their infants. A total of 36 mothers 15 to 21 years of age and their 4-month-old infants were videotaped in their homes during play, infant teaching, and bathing. Selman's "concepts of persons" interview, revised to an infant crying situation, was conducted at a second visit. During a third visit, multiple formal operations measures and an intellectual aptitude measure, the Raven Progressive Matrices, were administered. Data indicated that availability of certain formal operations is correlated with the quantity of verbal stimulation in mothers' teaching schemes. These data were, however, highly related to the effects of intellectual aptitude. By contrast, more advanced concepts of persons are associated with greater verbal stimulation and more accepting maternal behavior independent of intellectual aptitude. Cognitive-developmental status has different effects across caregiving situations; social reasoning is strongly related to bathing behavior, and the availability of certain formal operations is moderately related to teaching behavior. Findings are discussed in reference to explanatory models for widely reported deficiencies in adolescent maternal behavior. (Author/RH)