Mother-stranger discrimination in three-month-old infants and subsequent Gesell performance.

The amount of vocalization, motor activity, and smiling in response to vocal stimulation by the mother and by a stranger was recorded from 14 normal male infants when they were 3, 5, 7, and 9 months old. The Gesell Developmental Schedules were administered to them at age 9 months. High Gesell developmental quotient infants showed different vocalization and motor activity responses to the mother versus the stranger as early as 3 months. These differences diminished progressively to a minimum at 9 months. Low Gesell developmental quotient infants showed no differential responses to mother versus stranger. The results suggest that mother-stranger discrimination at age 3 months may be used as an indicator of subsequent cognitive development, and further suggest that bright babies may attain permanence for the mother's schema as early as 3 months of age.