Experiences disturbing the attachment of young mammals to their mothers, and of the mothers to the newborn, tend to delay and distort development in many respects. Does mental retardation in early childhood result from similar disorders in social behavior? Observations made in a series of "undifferentiated" cases suggest that it does when the security system provided by the family has failed to protect the infant from stress. The implications of this view for prevention and treatment are discussed.Abstract Teaser