Cognitive Development in Infancy

All 8 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's research suggested it reflects developing executive processes — working memory and inhibitory control — rather than a simple failure to represent the object's location. Other researchers have proposed additional explanations involving attention, motor factors, and task demands, making the A-not-B error a useful case study in how difficult it is to interpret a single infant behaviour.

Violation-of-expectation (VOE) paradigm

A method exploiting the fact that infants tend to look longer at unexpected or unusual events. Infants are shown a possible event and an unexpected or impossible one; if infants look longer at the impossible event, researchers interpret this as evidence that they represented an expectation about what should happen. However, longer looking is an indirect measure — it does not directly reveal the underlying mental representation — and whether such results reflect genuine conceptual knowledge, perceptual preferences, or something else remains an active methodological debate in infant cognition research.

Looking measures vs reaching measures

Infant cognition research uses two broad types of behavioural measure. Reaching tasks (Piaget's method) require infants to act on their understanding — searching, retrieving, or manipulating. Looking-time tasks (Baillargeon's VOE paradigm) infer understanding from how long infants attend to possible versus impossible events. An infant may appear to "know" something in a looking task while still failing an equivalent reaching task. This dissociation matters: it suggests that what a method reveals about cognition depends on which behavioural channel is measured, and that different methods can produce different estimates of when an ability first appears.

Core knowledge theory

Core knowledge theory (Spelke; Baillargeon) proposes that infants begin life with, or rapidly develop, implicit domain-specific systems for representing objects, agents, numbers, and space. These early representations are proposed to provide an initial framework that guides subsequent learning — contrasting with Piaget's constructivist account, in which knowledge is built through infants' interactions with the environment. The theory has been highly influential, but the evidence it rests on — primarily infant looking-time studies — remains debated.

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 — interpreted as evidence that the infant encoded and retained a representation of the observed action. Piaget dated deferred imitation to substage 6 (~18 months). Meltzoff showed deferred imitation of novel actions in 9-month-olds after a 24-hour delay, suggesting earlier representational capacity than Piaget's account allows.