Studies indicate that certain cognitive processes, the order of which is largely biologically controlled, begin as early as two months after birth. Up to six months of age, differences in motor and conceptual development are generally independent of the infant's rearing conditions and culture, but by one year of age, cultural differences affect intellectual development. From the early months on, the infant forms attachments to those who care for him or her, and on the basis of their behavior, begins to develop expectations of gratification, e.g., adult responses to cries of distress. Social smiling appears early, and by the latter part of the first year the baby may depend on the presence of familiar faces and become apprehensive in the presence of strangers.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.