Infancy

Brain Growth

Infancy is a period of rapid and significant growth in almost every sphere, including physical, cognitive, emotional, and social development. Neuroscientific, biological, genetic, and social science research has shown how the first 1,000 days (the antenatal period and the first 2 years of life) are foundational in terms of brain development. Brain development and the neural connections formed in this early period are central to later social, emotional, and cognitive development. However, advances in neuroscience show that the brain is maturing well into the 20s, considerably beyond the first 2 years of life.

Physical Development

There are marked differences in the rate at which individual infants develop physically, with genetic, environmental, and nutritional factors playing a role. On average, however, infants double their body weight every 4 months for the first year of their life. Yet within the individual infant, different parts of the body develop at different rates—for instance, the head, which is out of proportion to the rest of the body at birth, grows at a pace far slower than the trunk and limbs.

In line with the infant’s rapid skeletal and muscular growth, the capacity for motor activity increases rapidly during the first year and a half, and by 15 months, most infants are toddling. Perceptual development also occurs at a rapid rate. Depth perception, visual constancy (the ability to perceive an object as the same thing regardless of the perspective from which it is seen), and intrasensory integration (making sense of combinations of sounds, sights, sensations, odors, and tastes in combinations) develop during this time.

Cognitive Development

Examining the cognitive development of infants has intrigued philosophers, neurologists, and psychologists, resulting in numerous theories of cognitive development and the maturation of infants’ thinking. Perhaps the most influential of these is that of Jean Piaget, who posited that infants’ cognition is initially dominated by physical reactions to physical sensations (a foot being jerked away from being tickled) and that the capacity for symbolic representation (the ability to use mental images or words to think about things that are not within the immediate vision of the infant) develops later.

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