Cephalocaudal principle

The principle that growth follows a pattern that begins with the head and upper body parts and then proceeds down to the rest of the body.


Repetitive, cyclical patterns of behavior

Proximodistal principle

The principle that development proceeds from the center of the body outward.

Principle of hierarchical integration

The principle that simple skills typically develop separately and independently but are later integrated into more complex skills.

Principle of the independence of systems

The principle that different body systems grow at different rates.


The basic nerve cell of the nervous system.


The gap at the connection between neurons, through which neurons chemically communicate with one another.


A fatty substance that helps insulate neurons and speeds the transmission of nerve impulses.

Cerebral cortex

The upper layer of the brain.


The degree to which a developing behavior or physical structure is modifiable.

Sensitive period

A specific time when organisms are particularly susceptible to certain kinds of stimuli in their environment.


The degree of awareness an infant displays to both internal and external stimulation.

Rapid eye movement (REM) sleep

The period of sleep that is found in older children and adults and is associated with dreaming.

Sudden infant death syndrome (SIDS)

The unexplained death of a seemingly healthy baby.


Unlearned, organized, involuntary responses that occur automatically in the presence of certain stimuli.

Dynamic systems theory

A theory of how motor skills develop and are coordinated.


The average performance of a large sample of children of a given age.

Brazelton Neonatal Behavioral Assessment Scale (NBAS)

A measure designed to determine infants’ neurological and behavioral responses to their environment.

Nonorganic failure to thrive

A disorder in which infants stop growing due to a lack of stimulation and attention as the result of inadequate parenting.


The physical stimulation of the sense organs.


The sorting out, interpretation, analysis, and integration of stimuli involving the sense organs and brain.

Multimodal approach to perception

The approach that considers how information that is collected by various individual sensory systems is integrated and coordinated.


The action possibilities that a given situation or stimulus provides.