AP Syllabus focus:
‘In the sensorimotor stage, infants learn through sensory and motor interactions and develop object permanence.’
The sensorimotor stage is Piaget’s earliest period of cognitive development, when infants build knowledge by coordinating what they perceive with what they can do, gradually forming mental representations of the world.
Sensorimotor Stage: Core Idea
Piaget argued that from birth to about age two, cognition is grounded in sensory input (seeing, hearing, touching) and motor output (grasping, sucking, reaching). Thinking develops as infants discover how actions produce outcomes and begin to internalise these action patterns.
Sensorimotor stage: Piaget’s first stage of cognitive development (approximately birth–2 years) in which infants learn through sensory and motor interactions and increasingly use mental representations.
A central developmental shift is moving from “knowing by doing” to “knowing by thinking,” as infants become less dependent on immediate perception and more able to represent objects and events mentally.
How Infants “Think” in This Stage
Schemas function as action-based patterns (e.g., sucking, grasping) that are modified as infants encounter new situations.
Learning is often trial-and-error: infants repeat actions that produce interesting or satisfying effects.
Knowledge is initially present-focused: early on, out-of-sight often means “out-of-mind.”
Substages and Typical Milestones (Piaget)
Piaget described qualitative changes within the sensorimotor stage, often taught as six substages:
1) Reflexes (birth–1 month)
Behavior is dominated by innate reflexes (e.g., sucking, grasping).
Infants begin adapting reflexes to different contexts (e.g., varying sucking strength).
2) Primary circular reactions (1–4 months)
Repetition of actions centered on the infant’s own body (e.g., repeatedly sucking a thumb).
Accidental discoveries become intentional habits.
3) Secondary circular reactions (4–8 months)
Repetition shifts outward to the environment (e.g., shaking a rattle for sound).
Infants learn cause-and-effect through acting on objects.
4) Coordination of secondary circular reactions (8–12 months)
More goal-directed behavior: combining actions to achieve an outcome (e.g., pushing an obstacle aside to reach a toy).
Early signs of searching for hidden objects appear, but performance is inconsistent.
5) Tertiary circular reactions (12–18 months)
“Little scientist” experimentation: varying actions to see new results (e.g., dropping objects from different heights).
More flexible problem-solving emerges through active exploration.
6) Mental representation (18–24 months)
Internal, symbolic thought expands: infants can mentally “try out” solutions.
This supports more complex problem-solving even when actions are not immediately executed.
Object Permanence
A hallmark of this stage is the emergence of object permanence—the understanding that objects continue to exist even when they are not currently perceived.
This is a key example of how infants shift from relying on direct sensation to forming mental representations.
Object permanence: the understanding that objects continue to exist even when they cannot be seen, heard, or touched.
Infants’ performance on hiding tasks typically improves over the first two years, suggesting increasing ability to represent absent objects. A classic difficulty during the transition is the A-not-B error, in which an infant repeatedly searches for a hidden object in a previously rewarded location (A) even after seeing it moved to a new location (B), indicating limits in working memory, attention, and inhibitory control at that moment in development.
Why Object Permanence Matters
It reflects growing representational thought, not just improved motor skills.
It supports more stable expectations about the world (e.g., caregivers, toys, and routines exist even when not present).
It marks a broader shift toward internal cognition that becomes more prominent after the sensorimotor stage.
FAQ
They often use looking-time methods.
Violation-of-expectation: infants look longer at “impossible” events (suggesting an expectation about hidden objects).
Eye-tracking can show anticipatory gaze to where an object should reappear.
Deferred imitation is copying an observed action after a delay.
It suggests the infant formed a memory-based representation of the action, supporting Piaget’s claim that mental representation strengthens toward the end of the sensorimotor stage.
It can reflect competing demands on attention and control:
Weak working memory for the new location
Strong habit from prior success at location A
Immature inhibitory control, making it hard to override the old response
No. Timing varies due to differences in:
Task demands (reaching vs looking)
Motivation and fatigue
Individual differences in attention and executive control
These factors can shift when object permanence is observable.
Some evidence suggests competencies appear earlier than Piaget proposed.
Researchers argue that infants may possess earlier representations, but performance can be masked by limits in motor coordination, attention, or task structure rather than absence of understanding.
Practice Questions
Define object permanence and state the approximate age range in which it typically develops during the sensorimotor stage. (1–3 marks)
1 mark: Accurate definition of object permanence.
1 mark: Links it to objects continuing to exist when out of sight.
1 mark: Gives a reasonable age range within birth–2 years (e.g., emerges across the first two years).
Explain how cognitive abilities change from secondary circular reactions to mental representation in the sensorimotor stage. Refer to goal-directed behaviour and object permanence. (4–6 marks)
1–2 marks: Describes secondary circular reactions (repetition focused on effects on the environment).
1–2 marks: Explains increasing goal-directed behaviour (coordinating actions to reach goals).
1–2 marks: Explains mental representation and improved object permanence (using internal representations to understand hidden objects).
