ABSTRACT
INFANCY is a period of rapid change along biological and psychological continua. Infants’ major tasks are to grow and learn, which they accomplish at a rate unmatched at any other time in the life span. Infants typically double their length and quadruple their birthweight by 2 years of age. Although most of the neurons of the infant brain have been generated prior to birth, the arborization process through which the brain becomes interconnected is only beginning. Many of the infants’ early interactions with their environments are structured by reflexes that control vital functions, including their approach to food and avoidance of aversive stimuli. The infants’ motor responses, initially dominated by underlying reflexes, gradually come under intentional control. Gross uncoordinated action is slowly replaced by fine coordinated action. Infants’ sleep patterns change, with both alert states and deep sleep states gradually emerging, sleep periods increasing in length and rhythmicity, and the amount of daily sleep decreasing. The sensory systems, already functioning to varying extents before birth, continue to develop after birth, with the auditory and particularly visual systems maturing last. With increasing periods of alertness, infants quickly become active information processors, with learning occurring at breakneck speed. Although the basic structure of the infant’s temperament is in place early, the development of the emotional system and attachment responses awaits the emergence of the cognitive system. As motor, sensory, cognitive, and emotional development proceeds, infants progress toward becoming active, self-regulatory, and social beings.
