Cognitive Development in Infancy

All 7 Terms & Definitions

Sensorimotor stage (Piaget)

The first of Piaget's four stages, spanning birth to approximately 2 years. Intelligence is entirely practical — knowing the world through action and perception rather than mental representation. Piaget subdivided it into six substages tracing the development from reflexes through primary, secondary, and tertiary circular reactions to the onset of mental representation (substage 6, ~18–24 months).

Object permanence

The understanding that objects continue to exist when they are no longer perceptible. Piaget held that this is absent in infants under 4–8 months and fully consolidated around 18–24 months, as evidenced by search behaviour. The A-not-B error — searching where an object was previously hidden, not where it was just hidden — marks an intermediate stage around 8–12 months.

A-not-B error

The tendency of 8–12-month-old infants to reach for an object at a previously successful search location (A) even after watching it being hidden at a new location (B). Piaget interpreted this as evidence of incomplete object permanence. Diamond (1985) showed it reflects executive control — the infant knows where the object is but cannot inhibit the dominant reaching response.

Violation-of-expectation (VOE) paradigm

A method exploiting the fact that infants look longer at unexpected events. Infants are habituated to a possible event; then they see either the same event or a physically impossible one. Longer looking at the impossible event implies a violated expectation — i.e. knowledge of the underlying physical principle. Baillargeon used VOE to show object permanence at 3½ months, far earlier than Piaget's reaching-based evidence.

Core knowledge (Baillargeon)

The hypothesis that infants are born with — or develop very early — implicit domain-specific knowledge systems about objects, agents, number, and space. These systems are not constructed from sensorimotor action but constitute an initial framework that constrains and guides learning. Contrasts with Piaget's blank-slate constructivism.

Joint attention

The ability to coordinate visual attention with a social partner toward a shared external object — achieved through gaze following, pointing, and referential looking. Emerges reliably around 9–12 months. A prerequisite for language acquisition and theory of mind, and one of the earliest reliable markers distinguishing typical from atypical social-cognitive development.

Deferred imitation

The reproduction of a modelled action after a delay — evidence that the infant has formed and stored a mental representation of the action. Piaget dated deferred imitation to substage 6 (~18 months). Meltzoff showed deferred imitation of novel actions in 9-month-olds, again suggesting earlier representational capacity than Piaget's account allows.