The sensorimotor stage is the first of the four stages in Piaget’s theory of cognitive development, spanning birth to about two years.
During this stage, infants know the world through their senses and motor actions rather than through mental representation. Through repeated action, they gradually build a basic understanding of objects, space, causality, and time.
Key Characteristics of Sensorimotor Stage (birth to ~2 years):
- Sensory and Motor Exploration: Infants learn by using their senses (sight, touch, sound, etc.) and motor actions (grasping, crawling, etc.) to interact with the environment.
- Object Permanence: They develop the understanding that objects continue to exist even when out of sight — a major cognitive milestone.
- Cause and Effect (Causality): Infants begin to understand that their actions can cause specific outcomes (e.g., pressing a button makes a sound).
- Development of Schemas: Through repeated experiences, infants build basic mental frameworks (schemas) that help them understand and predict the world.
- Emergence of Symbolic Thought: Toward the end of this stage, infants begin to use mental representations and engage in simple pretend play (e.g., using a banana as a phone).
How do infants learn during the sensorimotor stage?
Infants learn through a process that integrates sensory processing (seeing, hearing, touching) and motor skills (grasping, crawling), allowing them to interact with and interpret their environment.
As they touch, see, hear, and move, they engage in exploration behavior, such as grasping objects, mouthing toys, or crawling toward sounds.
These repeated interactions form the basis of sensorimotor learning, where infants begin to recognize patterns and outcomes (e.g., shaking a rattle makes a sound).
Through this active engagement, infants gradually build schemas. Each schema is a mental structure that helps them organize and make sense of their experiences.
For example, an infant might develop a schema for “grasping” that can be adapted to different objects, or a schema for “dropping” that helps them explore gravity and cause-effect relationships.
This cycle of action and feedback is fundamental to cognitive development during the sensorimotor stage.
Why the sensorimotor stage matters
The sensorimotor stage is critical because it shows how early experience shapes brain development.
During this period, every touch, sound, and movement helps form neural connections that are essential for later cognitive growth.
It also lays the foundation for key abilities such as language, memory, and problem-solving.
These everyday moments are doing real cognitive work. Remembering a hidden toy builds memory, copying a sound builds language, and reaching for an object builds problem-solving: all skills used in later, more complex thinking.
Because of its foundational role, the sensorimotor stage is a key focus in parenting strategies, early childhood education, and developmental psychology research.
Understanding it helps caregivers and professionals support healthy development right from birth.
What To Look Out For In Your Child
As you navigate the early years of parenting, you’ll notice many little signs that your child is developing new ways of thinking and understanding the world.
One important milestone is object permanence —when your child realizes things (and people) still exist even if they’re not visible.
Your child stays calm as you leave the room. That’s confidence that you haven’t disappeared forever, just moved out of sight for now.
This understanding helps your child feel secure during separations, making transitions easier and helping them feel comfortable with other familiar caregivers.
Another big step you’ll observe is their growing understanding of cause and effect.
At first, it’s simple mischief. Deliberately dropping food or splashing water in the bath is your child testing what happens next.
As they get older, they’ll interact more purposefully with toys, like pressing a button repeatedly just to hear the sound.
These behaviors show they’re beginning to connect their actions with specific outcomes, a crucial part of their cognitive growth.
How does cognitive development progress from reflexes to symbolic thought in infancy?
Cognitive development in infancy begins with sensorimotor intelligence, where newborns interact with the world through basic reflexes such as sucking and grasping.
As infants grow, these reflexes evolve into more intentional behaviors, forming the foundation of mental schemas – organized patterns of action or thought used to understand and respond to experiences.
Through repeated exploration and interaction, these schemas become more complex.
Infants begin to understand cause-and-effect, develop object permanence, and eventually form internal mental representations of objects and events.
This marks the shift toward representational thought, where thinking is no longer tied to direct sensory input or physical actions.
Symbolic play begins by the stage’s end. Now children use one object to represent another, around 18 to 24 months, an early sign of abstract thought.
All of this cognitive growth is supported by rapid brain development, particularly in areas related to memory, problem-solving, and symbolic processing.
Developmental Milestones
The schemas constructed during this period provide the foundation for more complex and abstract thinking that will emerge in later stages.
The understanding of objects, space, causality, and time that develops during the sensorimotor stage serves as the basis for the child’s developing worldview and their capacity for reasoning and problem-solving.
1. Reflexes
- What It Means: Newborns respond to the world through automatic, inborn reflexes like sucking, grasping, and blinking, not yet under conscious control.
- When It Happens: Reflexive behavior dominates from birth to about 1 month, when babies react to stimuli rather than intentionally exploring.
- Why It’s Important: These reflexes help babies survive and form the foundation for the more coordinated, intentional actions of later substages.
- Signs to Watch For: Automatic sucking when something touches the mouth, or grasping a finger pressed into the palm, shows reflex pathways are active.
2. Imitation
- What It Means: Infants copy actions, expressions, or sounds they observe. Simple imitation appears early; more complex, delayed imitation follows later in the stage.
- When It Happens: Basic imitation appears in the first few months of life. Delayed imitation, once thought to start around 18–24 months, has been shown in infants as young as 14 months (Meltzoff, 1988).
- Why It’s Important: Imitation supports social behavior, language, and problem-solving, showing that infants can remember and reproduce what others do.
- Signs to Watch For: Look for copied gestures like clapping or pretend phone calls. Delayed imitation, mimicking something seen hours earlier, is a major milestone.
3. Object Permanence
- What It Means: The realization that objects continue to exist even when they’re out of sight.
- When It Happens: Piaget found infants rarely search for a hidden object before about 8 months. Search emerges from 8–12 months, and understanding is largely complete by 18–24 months.
- Why It’s Important: It’s the starting point for memory and for trusting that caregivers and objects remain constant even when out of view.
- Signs to Watch For: Babies enjoy peekaboo and search for hidden toys. They may cry when a caregiver leaves, not from forgetting them, but from knowing they still exist.
4. Cause and Effect
- What It Means: Infants recognize that specific actions lead to specific outcomes, like shaking a rattle making a sound, an early form of cause-and-effect reasoning.
- When It Happens: Babies show initial signs of grasping cause and effect between 4 and 8 months, and this understanding deepens throughout the stage.
- Why It’s Important: It builds early problem-solving and a growing sense of agency, and underlies learning theories like operant conditioning, where behavior is shaped by its consequences.
- Signs to Watch For: Babies drop toys repeatedly to see what happens, or press buttons and splash water, watching closely for the result.
5. The Start of Pretend Play
- What It Means: Using one object to stand for another, like pretending a banana is a phone, shows the onset of mental representation and imaginative play.
- When It Happens: Pretend play usually begins around 18 months and becomes more complex by age 2, as children use objects to represent other things.
- Why It’s Important: Imaginative play builds creative thinking and lays a foundation for language, as children act out scenarios and assign roles.
- Signs to Watch For: Watch for a bowl used as a hat, a box as a car, or simple scenarios like feeding a doll or role play.
Sub-Stages
The sensorimotor stage of development can be broken down into six additional sub-stages including:
- Reflexive Schemes: Newborns rely on innate reflexes like sucking, grasping, and blinking to interact with their environment. These automatic responses form the foundation for later voluntary behaviors.
- Primary Circular Reactions: Infants begin to repeat actions centered on their own body that bring pleasure, such as sucking their thumb. These behaviors are discovered by chance and then intentionally repeated.
- Secondary Circular Reactions: Babies start to focus on the external environment, repeating actions that produce interesting effects, like shaking a rattle. Learning becomes more about the outcome of interacting with objects.
- Coordination of Secondary Circular Reactions: Infants begin to combine actions purposefully to achieve goals, such as pushing a toy aside to grab another. This stage marks the beginning of intentional problem-solving.
- Tertiary Circular Reactions: Toddlers act like little scientists, experimenting with different actions to observe varied outcomes, such as dropping objects in new ways. This reflects growing curiosity and flexible thinking.
- Mental Representation: Children develop the ability to form mental images of objects and events, leading to symbolic thought and pretend play. They can now solve problems mentally rather than through trial-and-error.
1. Reflex Acts (Reflexive Schemes: 0–1 month)
In their first month, babies naturally react to the world around them through automatic behaviors called reflexes.
These aren’t actions they think about or plan—babies simply respond instinctively.
Common reflexes include sucking, grasping your finger tightly, and looking toward sounds or movements.
A familiar example is the rooting reflex. Gently stroke your baby’s cheek or lips, and they’ll automatically turn toward your hand and open their mouth, ready to feed.
This reflex helps newborns breastfeed and shows how babies are born with built-in responses to support survival and early development.
2. Primary Circular Reactions (1–4 months)
Between 1 and 4 months, babies start repeating simple actions with their own bodies that feel good or comforting.
For example, your baby might suck their thumb or kick their legs repeatedly because they enjoy the sensation.
Initially, these actions happen by accident, but your baby continues doing them because they find them pleasurable.
The term “circular” refers to how babies repeat these enjoyable actions again and again.
At this stage, they’re not focused on interacting with objects or achieving specific goals; they’re simply exploring and enjoying sensations that relate directly to their own body.
3. Secondary Circular Reactions (4–8 months)
Between 4 and 8 months, babies start exploring how their actions affect the world around them.
Unlike earlier months, when their actions mainly involved their own body, they now intentionally interact with external objects.
For example, your baby might accidentally shake a rattle and enjoy the sound it makes, then shake it again purposefully to hear it again.
Their focus is shifting. At this stage, their motivation moves from enjoying sensations to noticing interesting outcomes in the world.
They’re curious about how things work and begin to understand that their actions cause things to happen.
This growing awareness helps them discover that they can influence their environment, marking an important step in their development.
4. Co-ordinating Secondary Reactions (8–12 months)
From around 8 to 12 months, babies begin combining multiple actions to reach a specific goal, even when the solution isn’t immediately obvious.
They’re starting to use what they’ve learned to solve simple problems in a planned way.
Picture your baby wanting a toy just out of reach. If it’s sitting on a cloth, they might pull the cloth to bring the toy closer.
This shows they’re using one action (pulling the cloth) as a way to accomplish another action (grabbing the toy).
This ability to coordinate different actions is a big step forward.
They’re starting to think ahead. They now solve problems intentionally, by connecting one action to another.
It also helps them understand relationships between actions and outcomes, which is crucial for developing more advanced thinking skills.
Why Coordinating Actions Matters (8–12 Months):
At this stage, your baby’s ability to combine different actions is a big milestone because it means they’re starting to:
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Act intentionally: Your baby can now clearly use one action to achieve another, showing they have specific goals in mind when they act.
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Solve problems: They’re beginning to overcome simple challenges by using actions they’ve learned before in new ways, adapting and combining them to find solutions.
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Understand relationships: Your baby starts understanding how things relate to each other, like how objects and actions fit together in space and time, setting the stage for more advanced thinking and learning in the future.
5. Tertiary Circular Reactions (12–18 months)
Between 12 and 18 months, toddlers become little explorers, actively experimenting with objects around them to see what new effects or discoveries they can make.
Unlike earlier stages, when they mostly repeated known actions, now they’re curious about how and why things happen.
At this stage, your child deliberately tries different actions – like dropping toys from different heights, tipping over containers, or mixing things—to test outcomes.
They use trial-and-error to learn about their surroundings, driven by a natural interest in understanding and exploring the world in new ways.
Key characteristics of tertiary circular reactions:
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Curiosity and Exploration: Your child intentionally tries new ways of interacting with objects to see what different effects they can produce. They actively explore concepts like gravity or how objects move when dropped or thrown.
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Varied Actions and Testing: Instead of repeating the same action over and over, your child changes their approach to discover new outcomes. They might vary how high they drop a toy or how forcefully they push something, exploring the differences in results.
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Interest in Objects’ Qualities: Toddlers at this age start paying close attention to what makes objects unique. They want to understand objects’ specific characteristics, behaviors, and possibilities, viewing each object as something interesting and distinct in itself.
Examples of tertiary circular reactions:
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Dropping toys from different heights: Your child might repeatedly drop toys from various heights, noticing differences in the sound, speed, and how the objects land. This helps them explore how height affects falling.
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Tilting boxes to see what happens: They might tip or shake boxes at different angles to observe how items move or spill out. This teaches them about stability, balance, and spatial relationships.
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Testing which objects float or sink: During bath time, your toddler might experiment with different items to see which float and which sink, learning about buoyancy and water properties.
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Pouring water between cups: Your child might pour water from one container into another, watching closely how the water flows or fills differently shaped containers. This shows they’re exploring how liquids behave and beginning to understand concepts like volume.
6. Mental Representation (18–24 months)
Between 18 and 24 months, toddlers begin using symbolic thought—imagining things even when they’re not directly in front of them.
This is a huge developmental step that sets the stage for the next phase of growth.
At this age, your child can form mental pictures of people, objects, or events, allowing them to think about and remember things they can’t currently see.
Imaginative play follows soon after. Your child might now pretend a block is a phone, or a box is a car.
Symbolic thinking also means your child understands that things exist even when hidden from view (object permanence).
This skill lays the groundwork for future learning, supporting language development, creativity, and problem-solving abilities.
Critical Evaluation
Piaget’s account has held up well in some ways. It has been challenged sharply in others.
Piaget’s Observational Method
Aim: Piaget wanted to describe how intelligence and the object concept develop across infancy.
Method: He used the clinical-observational method. His sample was his own three children, observed daily at home over months.
He also ran small informal experiments, such as hiding a toy under a cloth to see how each child responded.
Results: The observations yielded the six-substage sequence above. Object permanence, deferred imitation, and symbolic play all appeared in a fixed order.
Conclusion: Infant cognition is actively constructed through the child’s own activity. The permanent object is an achievement, not a birthright.
The method’s strength is its richness. A replication by Corman and Escalona (1969) supported the substage order.
Its weakness is just as real. The sample was tiny, just three children, all Piaget’s own, from an unusually stimulating home.
Piaget also generated the theory and judged the data himself. No one else checked his interpretation.
The Core-Knowledge Challenge
A rival tradition took a different view. From the 1970s on, it argued that Piaget underestimated the infant.
The recurring problem is competence versus performance. Piaget’s search tasks demand motor skill, not just object knowledge.
Bower and Wishart (1972) tested this directly. They let an infant reach for an object, then switched off the lights.
Infrared cameras recorded what happened next. Infants kept reaching in the dark for up to 90 seconds. To them, the object still felt real.
Piaget’s own account said “out of sight” should mean “out of mind.” This showed otherwise.
Aim: Baillargeon asked whether infants much younger than Piaget’s 8-month mark represent hidden objects.
Method: In the classic drawbridge study, a screen rotated back and forth like a drawbridge. A solid box sat hidden in its path.
On impossible trials, the screen seemed to pass straight through the box (Baillargeon, Spelke, & Wasserman, 1985; Baillargeon, 1987).
A later study used a different hide. A tall carrot slid behind a screen with a window cut into it (Baillargeon & DeVos, 1991).
On impossible trials the carrot failed to appear in the window, though it should have.
Results: Infants as young as 3½ months looked longer at the impossible events. They never saw the whole object, yet still noticed.
Conclusion: Hidden objects are represented months earlier than Piaget’s search tasks could show. The problem was his method, not the infant’s mind.
Most researchers today read it this way. Piaget charted the infant’s growing ability to act on object knowledge accurately.
He underestimated the perceptual knowledge that comes first. That knowledge simply outstrips what a young infant can physically do about it.
Contemporary Research
Two lines of research since 2015 push the core-knowledge case further, asking not just when infants notice a hidden object’s persistence, but what that knowledge is for.
Surprise as an Engine of Learning
Stahl and Feigenson (2015) asked a different question. What is early object knowledge actually for?
Aim: To test whether infants use surprise itself as a cue for what to learn next.
Method: Published in Science, the study showed 11-month-olds (N = 110) objects that broke or matched physical rules. One ball seemed to pass through a wall.
Results: Infants learned more about the rule-breaking objects, and explored them more.
They even tested them in matching ways: banging a wall-passing ball, but dropping one that seemed to defy gravity.
Conclusion: Surprise acts like a wedge. It points infants toward exactly the property that was violated, and tells them what is worth learning.
Logical Inference Over Hidden Objects
Cesana-Arlotti and colleagues (2018) pushed the question further still. Can infants reason logically about something they cannot see?
Aim: To test whether pre-verbal infants can perform a disjunctive syllogism.
This is reasoning of the form: the hidden object is either the first candidate or the second; it is not the first; so it must be the second.
Infants aged 12 and 19 months watched hidden objects revealed one candidate at a time. Only one answer made sense.
Results: Infants looked longer, and their pupils dilated more, when the reveal broke the rule.
That mirrors effortful adult reasoning.
Conclusion: Toddlers may perform elementary logical inference over hidden objects, without language.
It is one striking study, not yet a settled consensus. Read with Baillargeon et al.’s (2016) review of two decades of evidence, it points the same way.
Infant object cognition is more structured, and used more actively, than Piaget’s method could ever show.
Where This Leaves the Theory
The sequence of substages has held up well. Object permanence, deferred imitation, and symbolic play still appear in the order Piaget described.
A replication by Corman and Escalona (1969) supported that order, and it looks broadly universal across cultures.
What has not held up is the timetable. Object knowledge, measured by looking time, shows up months before Piaget’s search tasks could detect it.
Culture shifts the pace of development. It does not shift the order.
The core-knowledge tradition also rebalances an old debate. Infants seem to arrive with more built-in structure than Piaget’s constructivism allowed.
That does not overturn construction. It shifts how much of the object concept is built, versus simply brought along at birth.
The stage is best read as an accurate map of behavioral milestones. It was once attached to a timetable that ran too late for the competence underneath.
Real-World Applications
Piaget never meant the sensorimotor stage as a purely academic timetable. It has shaped how adults support very young children in several fields.
Early-Years Education and Play-Based Practice
The sensorimotor infant knows the world through action, not instruction. Learning works best when it is active and self-directed (Piaget, 1964).
That is why nurseries offer open-ended “heuristic play” with everyday objects like wooden spoons and tins.
It lets an infant repeat real actions. This is the same pattern as the circular reactions above, not a single-purpose toy.
A wooden spoon or a tin can be banged, dropped, and shaken in as many ways as a baby likes.
Games built around the stage’s own milestones are staples of infant-room curricula for exactly this reason.
Peekaboo and hide-and-reveal play scaffold object permanence.
A lever that produces a sound matches the secondary circular-reaction substage.
Turn-taking and pretend routines anticipate the symbolic function that matures at the stage’s close.
Developmental Assessment and Early Intervention
The six substages were formalized into a clinical tool, the Uzgiris-Hunt Ordinal Scales of Psychological Development (Uzgiris & Hunt, 1975).
It tracks progress across several sensorimotor domains, rather than producing one score against age norms.
This ordinal, stage-based approach has helped map atypical development.
Dunst (1988) applied the scales to 30 infants with Down syndrome and 12 typically developing infants.
The infants with Down syndrome took significantly longer to move between stages, even accounting for their slower overall pace.
Order was preserved even where rate and timing were not.
Lösche (1990) compared home-movie footage of autistic infants and typically developing infants, from 4 to 42 months.
Sensorimotor and action development diverged from around the second year onward.
The difference was not simply a delay.
It concentrated in actions that need a mental representation of the intended outcome, the same capacity Piaget locates in the final substage.
Findings like these feed into early intervention. They flag representational milestones, like deferred imitation, as markers worth watching alongside standard assessment.
How To Help Your Child During This Stage
The sensorimotor stage (birth to ~2 years) is when babies learn through movement and sensory exploration.
You don’t need fancy toys — everyday interactions and simple materials can have a big impact.
It’s about creating opportunities for hands-on exploration, movement, and meaningful interaction.
🧠 1. Stimulate the Senses with Diverse Materials
Infants learn by processing sensory input — through touch, sight, sound, smell, and taste.
Offering a variety of sensory experiences strengthens their brain connections and builds foundational understanding of the world.
What to do:
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Provide materials with different textures (e.g., soft fabric, rubbery teethers, wooden spoons).
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Let them play with sound-producing toys like rattles, musical instruments, or crinkly paper.
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Create safe taste exploration by offering age-appropriate foods with varied flavors and textures.
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Use sensory bins with rice, pasta, or water (supervised) to explore through scooping, pouring, and feeling.
🦶 2. Support Gross and Fine Motor Development
Movement is central to sensorimotor learning.
As babies learn to control their bodies, they explore more freely and with greater intention.
What to do:
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Offer tummy time daily to build core strength and prepare for crawling.
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Place toys just out of reach to encourage reaching, rolling, and crawling.
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Provide opportunities to stand and cruise along furniture for older infants.
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Use stacking rings, nesting cups, or shape sorters to promote fine motor skills and coordination.
👁️ 3. Build Object Permanence Through Simple Games
Developing object permanence — knowing that things exist even when out of sight — is a key cognitive leap in this stage.
What to do:
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Play peekaboo with your hands, a cloth, or a favorite toy.
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Hide small toys under cups or behind furniture and encourage your child to find them.
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Use picture books with flaps or windows that “reveal” hidden images.
Why it matters:
This helps babies understand that people and objects don’t vanish just because they’re out of sight, which builds memory and trust.
🧪 4. Encourage Cause-and-Effect Learning
Infants begin to understand that their actions can influence the environment.
This is crucial for learning agency, problem-solving, and scientific thinking.
What to do:
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Let them press buttons that make sounds, flip light switches, or turn knobs.
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Set up water play with cups, sponges, and floating toys to experiment with pouring and squeezing.
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Give toys that react (e.g., pop-up toys, wind-up animals, stack-and-drop games).
Why it matters:
These repeated experiments help children learn predictability and control, forming early problem-solving skills.
🗣️ 5. Talk, Sing, and Engage in Social Interaction
Language and cognition develop together. Even before they speak, babies are learning how communication works through imitation, tone, rhythm, and turn-taking.
What to do:
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Narrate daily activities with rich, descriptive language.
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Sing songs with hand motions, like “Itsy Bitsy Spider” or “Wheels on the Bus.”
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Imitate your baby’s coos, gestures, or facial expressions to show them their communication has value.
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Read simple picture books, even if they just mouth or point at the pages.
Why it matters:
These interactions build social bonds, strengthen language processing, and teach basic conversation patterns.
🎭 6. Introduce Symbolic and Pretend Play (18–24 Months)
Toward the end of the sensorimotor stage, toddlers begin to use objects symbolically — an important sign of emerging abstract thinking.
What to do:
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Offer open-ended objects for imaginative use: blocks, cups, cardboard boxes.
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Encourage pretend scenarios (e.g., feeding a doll, talking on a toy phone).
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Join in! Modeling imaginative play supports language, empathy, and creativity.
Why it matters:
Symbolic thought underlies future skills like storytelling, reading, and problem-solving.
🧸 7. Provide Safe, Repetitive Experiences
Children in this stage learn best through repetition. Doing the same action again and again builds understanding and confidence.
What to do:
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Allow them to repeat actions like dropping spoons, knocking over blocks, or splashing in water.
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Rather than rushing to interrupt or correct, observe and support their process.
💡 Final Thought:
The most powerful way to support sensorimotor development is to be present, responsive, and playful.
Follow your child’s lead, create a safe space to explore, and turn everyday routines — diaper changes, meals, bath time — into opportunities for connection and learning.
Key Takeaways
- Sensorimotor Stage: Piaget’s first stage of cognitive development, from birth to about two years, when infants know the world through senses and motor action rather than mental representation.
- Six Substages: Development moves from reflexes, through primary, secondary, and tertiary circular reactions, to full mental representation by 18–24 months.
- Object Permanence: The central achievement of the stage; search behavior for hidden objects emerges around 8–12 months and is largely complete by 18–24 months.
- A-not-B Error: Around 8–12 months, infants who find a toy at one hiding place keep searching there even after watching it hidden somewhere new.
- Modern Evidence: Looking-time studies (Baillargeon, 1987) show infants represent hidden objects months earlier than Piaget’s search tasks suggested, though the substage sequence itself has held up well.
- Symbolic Thought: Deferred imitation and pretend play emerge near the stage’s close, marking the shift into representational thinking.
References
Baillargeon, R. (1987). Object permanence in 3½- and 4½-month-old infants. Developmental Psychology, 23(5), 655-664.
Baillargeon, R., & DeVos, J. (1991). Object permanence in young infants: Further evidence. Child Development, 62(6), 1227-1246.
Baillargeon, R., Scott, R. M., & Bian, L. (2016). Psychological reasoning in infancy. Annual Review of Psychology, 67, 159-186.
Baillargeon, R., Spelke, E. S., & Wasserman, S. (1985). Object permanence in five-month-old infants. Cognition, 20(3), 191-208.
Bower, T. G. R., & Wishart, J. G. (1972). The effects of motor skill on object permanence. Cognition, 1, 28-35.
Cesana-Arlotti, N., Martín, A., Téglás, E., Vorobyova, L., Cetnarski, R., & Bonatti, L. L. (2018). Precursors of logical reasoning in preverbal human infants. Science, 359(6381), 1263-1266.
Corman, H. H., & Escalona, S. K. (1969). Stages of sensorimotor development: A replication study. Merrill-Palmer Quarterly of Behavior and Development, 15(4), 351-361.
Dunst, C. J. (1988). Stage transitioning in the sensorimotor development of Down’s syndrome infants. Journal of Intellectual Disability Research, 32(5), 405-410.
Flanders, M., Tillery, S. I. H., & Soechting, J. F. (1992). Early stages in a sensorimotor transformation. Behavioral and Brain Sciences, 15(2), 309-320.
Lösche, G. (1990). Sensorimotor and action development in autistic children from infancy to early childhood. Journal of Child psychology and Psychiatry, 31(5), 749-761.
Meltzoff, A. N. (1988). Infant imitation after a 1-week delay: Long-term memory for novel acts and multiple stimuli. Developmental Psychology, 24(4), 470-476.
Piaget, J. (1952). The origins of intelligence in children. New York: International Universities
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Piaget, J. (1954). The construction of reality in the child. New York: Basic Books.
Piaget, J. (1964). Part I: Cognitive development in children: Piaget development and learning. Journal of research in science teaching, 2(3), 176-186.
Spelke, E. S. (2000). Core knowledge. American Psychologist, 55(11), 1233-1243.
Stahl, A. E., & Feigenson, L. (2015). Observing the unexpected enhances infants’ learning and exploration. Science, 348(6230), 91-94.
Uzgiris, I. C., & Hunt, J. M. (1975). Assessment in infancy: Ordinal scales of psychological development. University of Illinois Press.
