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Developmental Psychology: Lifespan Development · Development

Infancy: Cognitive Development

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On this page 7 sections
  1. In 30 seconds
  2. Why this matters
  3. The college version
  4. Eli explains
  5. Worked example
  6. Key takeaway
  7. Study tools

In 30 seconds

Piaget described infancy as the sensorimotor stage (birth to about age 2), in which infants build knowledge through sensory and motor actions and gradually develop mental representation and . Language emerges along a typical sequence—cooing, babbling, first words, then two-word combinations—supported by biological readiness and social interaction. Infant exists from early in life, though adults cannot recall infancy (infantile amnesia). The explains these changes as gradual improvements in attention, speed, and memory rather than distinct stages.

Why this matters

Clinicians and educators monitor communication—expecting babbling, first words, and word combinations within broad ranges—and refer for hearing or speech-language evaluation when a child's trajectory falls well outside typical patterns (assessment, not diagnosis). Nurses and allied-health providers support language by coaching caregivers to use infant-directed speech, respond to vocalizations, and talk and read with infants. Age-appropriate care includes simple explanations, familiar caregivers and objects to reduce distress, and recognizing that milestones vary with culture, multilingual environments, and individual experience—always deferring to local clinical guidelines.

The college version

1. Piaget's Sensorimotor Stage and Object Permanence

Piaget's first stage (birth to roughly age 2) has six substages built on circular reactions—repeating an action because of its result. Primary circular reactions (1–4 months) repeat body actions (sucking the thumb); secondary circular reactions (4–8 months) repeat actions that affect objects (shaking a rattle); tertiary circular reactions (12–18 months) deliberately vary actions to see new outcomes. Near the end, infants achieve mental representation—internal images or symbols—shown by deferred imitation (copying after a delay). Object permanence, understanding that objects exist when out of sight, develops gradually; Piaget noted the A-not-B error, in which an infant searches in an object's previous location rather than where they just saw it hidden. Later research (e.g., Renée Baillargeon's violation-of-expectation studies) suggests infants grasp object permanence earlier than Piaget proposed; the stage account remains a useful framework with known limits.

2. Language Development

Language emerges in a broadly typical sequence: cooing (vowel sounds, ~2 months), babbling (repeated syllables like "ba-ba," ~6 months), first words (~12 months, often holophrases where one word conveys a whole idea), and two-word "telegraphic" speech (~18–24 months, e.g., "more juice"). Receptive language (understanding) runs ahead of productive language (speaking). Nativist views (Noam Chomsky's language acquisition device) emphasize inborn capacity; behaviorist views emphasize reinforcement; interactionist views emphasize social interaction and infant-directed speech (the higher-pitched, slowed "caregiver speech"). Most contemporary accounts combine biological readiness with rich social and cultural input.

3. Memory and the Information-Processing Approach

Infants show memory early: Rovee-Collier's mobile task showed that 2- to 3-month-olds kick to move a mobile and remember the contingency days or weeks later—implicit (nonverbal) memory. Explicit, declarative memory develops more slowly, and infantile amnesia (the typical inability to recall events before about age 2–3) is linked to the maturing hippocampus and the absence of language and a sense of self. The information-processing approach describes growth as continuous improvement in attention, processing speed, working-memory capacity, and strategy use—measured with habituation (losing interest in a repeated stimulus) and dishabituation (renewed attention to a new stimulus). Unlike Piaget's stages, it emphasizes gradual, quantitative change.

How it works

  1. Infants act on the world and notice results, forming schemes.
  2. Repeated actions (circular reactions) refine these schemes across the substages.
  3. Infants coordinate senses and actions, then internalize them as mental images.
  4. Object permanence emerges as representation develops, enabling search for hidden objects.
  5. In parallel, social and biological factors drive language from cooing to sentences.
  6. Attention, speed, and memory improve continuously, supporting all of the above.

Common confusions

Do not confuseWithDifference
Object permanenceA-not-B errorPermanence is the concept; the A-not-B error is an incomplete grasp of it early on
Sensorimotor stageInformation-processing approachStages are qualitative leaps; information processing describes gradual gains
Receptive languageProductive languageUnderstanding runs ahead of speaking
Infantile amnesiaPoor infant memoryInfants remember; adults later cannot consciously retrieve those early memories
CorrelationCausationCaregiver talk and vocabulary correlate; experiments cannot isolate a single cause

Memory aids

S-O-L-M-I — "Sensors Open Language, Memory Inside": Sensorimotor stage, Object permanence, Language, Memory, Information-processing—the five key ideas of infant cognition.

Quick review

Topic Recap

Infant cognition grows from action-based knowing (Piaget's sensorimotor stage) to mental representation and object permanence, alongside a typical language sequence and early, mostly implicit memory. The information-processing approach complements the stage view by describing continuous improvements in attention, speed, and memory. All accounts are frameworks with strengths and limits; milestones are broad patterns influenced by biology, relationships, culture, and experience.

Knowledge Check

  1. What are the three types of circular reactions, and when do they appear?
  2. What is the A-not-B error and what does it reveal?
  3. Order the language milestones: two-word speech, babbling, first words, cooing.
  4. What does Rovee-Collier's mobile task demonstrate?
  5. How does the information-processing approach differ from Piaget's stage theory?

Answers and Rationales

  1. Primary (1–4 months, body-focused), secondary (4–8 months, object-focused), tertiary (12–18 months, deliberate variation)—they trace the growth of intentional action.
  2. Searching for a hidden object in its previous location rather than where it was just seen; it reveals that object permanence and location memory are still incomplete.
  3. Cooing → babbling → first words → two-word speech (receptive language runs ahead throughout).
  4. That infants as young as 2–3 months form and retain implicit memories of action-consequence links.
  5. Information processing describes continuous, gradual gains in attention, speed, and memory; Piaget described discrete qualitative stages.
Eli, the EliExplains learning guide

Eli explains

The same idea, in plain words

Explain it like I’m 10

Think of an infant's mind as a video game where the player at first only knows buttons that make things happen right now—sucking, looking, grabbing. In Piaget's sensorimotor stage, thinking is "out of sight, out of mind": the baby knows only what they directly sense and do. Slowly they learn the game's rules (schemes) and gain the ability to save a mental image of an object after it leaves the screen—that is object permanence, like realizing a hidden character still exists. Language is the upgrade that lets them name things without touching them. The information-processing approach describes the same progress differently—hardware getting faster and memory bigger, little by little, rather than unlocking levels. This stops being exact because a baby is not following a fixed script: culture, caregiver talk, and temperament all shape the timing.

Simple Example

A 6-month-old reaches for a partly hidden toy but stops when it is fully covered (no object permanence yet). By 12–18 months, the same child searches for the toy even when fully hidden, and by age two can find it after several hidden moves—showing emerging mental representation.

Worked example

  1. Piaget observed his own children and others to build the sensorimotor account—rich descriptions from small, culturally specific samples that may have underestimated infant abilities.
  2. Rovee-Collier's mobile and train experiments (1970s–80s) demonstrated infant memory using operant kicking, a measure of implicit memory; they show correlation between age and retention and cannot be generalized beyond lab settings.
  3. Violation-of-expectation studies (Baillargeon and colleagues) inferred earlier object permanence from longer looking; critics note longer looking may reflect surprise rather than full conceptual understanding.
  4. Methodological note: habituation and looking-time measures are indirect—they index attention, not necessarily conscious knowledge—and describe typical patterns and ranges, not fixed timetables.

Key takeaways

  • High yield: The sensorimotor stage spans birth to ~2 years and is built on primary, secondary, and tertiary circular reactions.
  • High yield: Object permanence develops gradually; the A-not-B error marks incomplete object permanence.
  • High yield: Language sequence: cooing → babbling → first words (~12 months) → two-word speech (~18–24 months).
  • High yield: Receptive language precedes productive language.
  • High yield: Infant memory exists early (Rovee-Collier); infantile amnesia reflects immature explicit memory.
  • The information-processing approach emphasizes continuous, gradual change rather than stages.
  • Habituation and dishabituation measure attention and novelty detection in infants.

Keep learning

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Practice Developmental Psychology: Lifespan Development

This lesson has no separate scored set. Practice draws from the subject’s question bank.

Study tools & related lessonsYou’ll learn to · Key vocabulary · Related

You’ll learn to

  • Describe Piaget's sensorimotor stage and its major substages.
  • Explain object permanence and how later research refined Piaget's account.
  • Trace typical language milestones from cooing to two-word speech.
  • Contrast the information-processing approach with Piaget's stage theory and summarize infant memory.

Key vocabulary

Piaget sensorimotor stage
First stage (birth–2 years) where knowing happens through senses and actions
Object permanence
Understanding objects exist when out of sight
Language development
Cooing, babbling, first words, two-word speech
Memory
Retention of experience (implicit vs explicit)
Information-processing approach
Cognition as gradual gains in attention, speed, memory

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