This study explored the relationship between the mother-infant interaction and the concurrent perceptual-cognitive and intellectual status of the infant. One hundred and eight-nine 12-week-old infants were given a battery of perceptual-cognitive tasks, including the Mental Developmental Index (MDI) of the Bayley Scales, the Corman-Escalona Scales of Object Permanence, and an attention task measuring response decrement and recovery. Data from these tests failed to show any sex or social class differences. However, the MDI was affected by birth order with first borns showing superior performance. In general, these three measures of perceptual-cognitive ability were unrelated. Mother-infant interactional data were collected and analyzed on three levels; frequency distributions, determination of simultaneous behaviors, and directed interactional behavior. The third level of anlaysis yielded more conclusive results concerning relationships between maternal behavior and infant performance. These findings suggest that specific contingencies between maternal and child behaviors are more informative than simple frequencies of behavioral occurrences, and that mother-infant interactional behavior is related to the young infant's cognitive status. (Author/SB)