The Sensorimotor Stage: How Infants (0-2 Years) Learn Through Senses and Actions

Watch a seven-month-old drop a spoon from a high chair, wait, then drop it again. This is not carelessness – it is science. The infant is testing gravity, cause and effect, and the reliability of the physical world. This kind of hands-on, sensory-driven learning is exactly what Jean Piaget described as the sensorimotor stage – the first and most foundational phase of cognitive development, spanning from birth to approximately two years of age. Long before a child can form a sentence or hold a thought in the abstract, they are busy building intelligence through touch, movement, sight, taste, and sound.

What is the sensorimotor stage? 🔗

The sensorimotor stage is the first of Piaget’s four stages of cognitive development. According to a review published on NIH’s NCBI, this is the period when children master two core phenomena: causality – the understanding that actions produce outcomes – and object permanence – the understanding that things continue to exist even when out of sight. Infants and toddlers use their senses and motor abilities to manipulate their surroundings and learn about the environment.

Piaget named this stage “sensorimotor” deliberately. Early intelligence in infancy appears directly from sensory perceptions and motor activities – touching, sucking, staring, grasping, banging. The child relies almost entirely on direct physical contact with the world. There is no abstract reasoning, no language-based thought, and no ability to mentally represent absent objects – at least not initially. All of that develops gradually across six distinct substages.

How infants learn: schemas, assimilation, and accommodation 🔗

To understand what is happening cognitively during this stage, it helps to understand how Piaget thought infants organize knowledge. He used the term schema to describe a mental framework for understanding and responding to the world. Children develop schemas through two processes: assimilation and accommodation. Assimilation means fitting new information into an existing schema – for example, a baby who already knows how to suck a bottle might try to suck a toy in the same way. Accommodation means updating or expanding a schema when new information doesn’t fit – realizing the toy behaves differently and adjusting the action accordingly.

This cycle of action, feedback, and adjustment is how infants construct their understanding of the world – not by being taught, but by actively doing and experiencing.

The six substages of sensorimotor development 🔗

Piaget subdivided the sensorimotor period into six substages, each building on the skills gained in the previous one. Together, they trace a remarkable journey from purely automatic responses at birth to deliberate, symbolic thinking by age two.

Substage 1: Reflexes (birth to 1 month) 🔗

Newborns arrive with a set of built-in reflexes – sucking, rooting, grasping, and startling. These automatic responses become more deliberate with practice, forming the very first raw material for cognitive development. When a ball touches an infant’s cheek and is automatically sucked, the infant is already beginning to connect sensation with action.

Substage 2: Primary circular reactions (1 to 4 months) 🔗

In this substage, infants start repeating actions that involve their own bodies and produce pleasurable results. Sucking a thumb, kicking legs, staring at their own hands – these are called primary circular reactions because they are centered on the infant’s own body. These repetitive actions help infants learn about their own bodies and the consequences of their movements. If something feels good or interesting, the infant tries to recreate it.

Substage 3: Secondary circular reactions (4 to 8 months) 🔗

Now the infant’s attention turns outward. Actions are no longer confined to the body – they begin to involve objects and people in the environment. Repeated motion brings particular interest as the infant is able to bang two lids together or shake a rattle and laugh. These are called secondary circular reactions because the infant is responding to effects outside of themselves. The child is delighted by their ability to make things happen and will repeat the action to keep the interesting outcome going.

Substage 4: Coordination of secondary circular reactions (8 to 12 months) 🔗

This substage marks a major cognitive shift: intentional, goal-directed behavior. The infant combines basic reflexes and uses planning and coordination to achieve a specific goal – for example, crawling across the room, reaching under a table, and grabbing a toy car. The infant is now coordinating both internal thinking and external action to pursue a desired result. This is also the period when object permanence begins to emerge, typically around 8 months, as infants start searching for hidden objects rather than accepting that they have simply ceased to exist.

Substage 5: Tertiary circular reactions (12 to 18 months) 🔗

The toddler at this stage is often described as a “little scientist.” The toddler explores the world in a trial-and-error manner, using both motor skills and planning abilities – for example, throwing a ball down the stairs just to see what happens. Unlike the earlier circular reactions where infants repeated the same action, here they deliberately vary their actions to observe different outcomes. It is active, exploratory experimentation.

Substage 6: Beginning of representational thought (18 to 24 months) 🔗

This is the culminating achievement of the sensorimotor stage. The toddler now has a basic understanding that objects can be used as symbols, can solve problems using mental strategies, remember something heard days before and repeat it, and engage in pretend play. Crucially, the child can now think through a problem mentally before acting on it – a capacity that was entirely absent at birth. At 18 months, symbolic play expands beyond the self: a child may attempt to feed a toy alongside themselves, or imitate household activities. This marks the transition from purely physical knowing to the beginning of mental representation.

Object permanence: the most significant milestone 🔗

Object permanence – the understanding that objects continue to exist even when they cannot be seen, heard, or touched – is widely considered the defining cognitive achievement of the sensorimotor stage. In this stage, according to Piaget, the development of object permanence is one of the most important accomplishments. In the early months of life, “out of sight” is genuinely “out of mind.” Hide a toy under a blanket in front of a three-month-old and they will show no interest in looking for it – as far as their cognitive system is concerned, the toy no longer exists.

By around 8 months, this begins to change. Object permanence is an essential building block for working memory, language development, and emotional attachment. It also explains why peek-a-boo is so captivating to young infants – the reappearance of a face genuinely surprises them – and why, as object permanence develops, babies lose interest in the game. The magic disappears because they now know the face was always there.

One well-known limitation associated with this development is called the A-not-B error. Even after infants begin to understand object permanence, they often search for a hidden object in the location where they previously found it (location A) rather than where they just watched it being hidden (location B). This tells us that early object permanence is still tied to specific actions and memories of prior success, rather than a fully flexible mental model of the object.

The dawn of symbolic thinking 🔗

Alongside object permanence, the emergence of symbolic or representational thought in substage 6 marks another profound transition. By the end of the sensorimotor stage, around 18 to 24 months, children engage in symbolic play, demonstrating their ability to use one object to represent another – an early sign of abstract thinking. A block becomes a car. A wooden spoon becomes a microphone. A cardboard box becomes a house. The child is no longer limited to acting on the physical world – they can now mentally represent it.

Near the end of the sensorimotor stage, infants also reach the milestone of early language development – a sign that they are developing symbolic abilities. Words are, after all, symbols – sounds that stand in for objects, people, and ideas. The capacity to use language grows directly from the same cognitive foundation being constructed throughout these two years of sensory and motor exploration.

Why this stage matters beyond infancy 🔗

The sensorimotor stage is not just a phase that children pass through – it is the foundation on which all later cognitive development rests. Every touch, sound, and movement during this period helps form neural connections that are essential for later cognitive growth, laying the groundwork for language, memory, and problem-solving. The schemas constructed during these two years become the mental frameworks children use for thinking, reasoning, and learning in school and beyond.

For educators and caregivers working with young children – particularly those with intellectual disabilities or developmental delays – understanding the sensorimotor stage is especially important. Nearly 53 million children worldwide have identifiable developmental delays, and many of these affect the very sensorimotor processes Piaget identified as foundational. Recognizing where a child is within these six substages helps caregivers provide targeted, appropriate stimulation – whether through tactile play, object permanence games like peek-a-boo, or activities that encourage imitation and early symbolic play.

It is also worth noting that while Piaget’s framework remains foundational, modern researchers have found that even very young children understand objects and how they work long before they have experience with those objects – suggesting that infants may be more cognitively capable than Piaget originally estimated. The timetables he proposed are now understood as approximate guides rather than fixed rules, and individual variation is significant.

What do you think? If an infant’s earliest learning is entirely dependent on sensory and physical experience, how might limited mobility or sensory impairment affect the cognitive milestones described in this stage? And given that symbolic thinking emerges from physical exploration, what does that tell us about the role of play in early childhood education?

References

1. https://www.simplypsychology.org/sensorimotor.html
2. https://www.ncbi.nlm.nih.gov/books/NBK537095/
3. https://web.cortland.edu/andersmd/piaget/sms.html
4. https://iastate.pressbooks.pub/individualfamilydevelopment/chapter/cognitive-development-piaget-and-the-sensorimotor-stage/
5. https://courses.lumenlearning.com/suny-lifespandevelopment/chapter/piaget-and-the-sensorimotor-stage/
6. https://content.one.lumenlearning.com/introductiontopsychology/chapter/9-2-4-learn-it-the-sensorimotor-stage/
7. https://viva.pressbooks.pub/topicalchilddev/chapter/piagets-sensorimotor-stage/
8. https://opentextbooks.concordia.ca/lifespandevelopment/chapter/3-6-piaget-and-the-sensorimotor-stage/
9. https://en.wikipedia.org/wiki/Piaget%27s_theory_of_cognitive_development
10. https://socialsci.libretexts.org/Courses/Western_Technical_College/ECE:_Infant_and_Toddler_Development/05:_Cognitive_and_Language_Development_in_Infancy_and_Toddlerhood/5.02:_Piaget-_Sensorimotor_and_Preoperational_Stages
11. https://www.webmd.com/children/piaget-stages-of-development
12. https://pxdocs.com/motor-milestones/sensorimotor-stage/
13. https://openbooks.library.baylor.edu/lifespanhumandevelopment/chapter/chapter-9-1-cognition-in-infancy-and-childhood/