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The Sensorimotor Stage of Cognitive Development

, updated 2018

The sensorimotor stage is the first of the four stages in Piaget's theory of cognitive development (1954, 1964). It extends from birth to approximately 2 years, and is a period of rapid cognitive growth.

During this period, infants develop an understanding of the world through trial and error using their senses and actions (i.e., motor movements). Through the processes of assimilation and accommodation actions become progressively adapted to the world.


From careful observation of his own children (Jacqueline, Lucienne and Laurent) Piaget (1952) concluded that thought developed through 6 sub stages during the sensorimotor period.

Reflex Acts

The first substage (first month of life) is the stage of reflex acts. The neonate responds to external stimulation with innate reflex actions. For example, if you brush a baby’s mouth or cheek with your finger it will suck reflexively.

Primary Circular Reactions

The second substage is the stage of primary circular reactions. The baby will repeat pleasurable actions centred on its own body.

For example, babies from 1 – 4 months old will wiggle their fingers, kick their legs and suck their thumbs. These are not reflex actions. They are done intentionally – for the sake of the pleasurable stimulation produced.

Secondary Circular Reactions

Next comes the stage of secondary circular reactions. It typically lasts from about 4 – 8 months. Now babies repeat pleasurable actions that involve objects as well as actions involving their own bodies. An example of this is the infant who shakes the rattle for the pleasure of hearing the sound that it produces.

Co-ordinating Secondary Schemes

The fourth substage (from 8 – 12 months) is the stage of co-ordinating secondary schemes. Instead of simply prolonging interesting events, babies now show signs of an ability to use their acquired knowledge to reach a goal.

For example the infant will not just shake the rattle, but will reach out and knock to one side an object that stands in the way of it getting hold of the rattle.

Tertiary Circular Reactions

Fifth comes the stage of tertiary circular reactions. These differ from secondary circular reactions in that they are intentional adaptations to specific situations. The infant who once explored an object by taking it apart now tries to put it back together.

For example, it stacks the bricks it took out of its wooden truck back again or it puts back the nesting cups – one inside the other.

Symbolic Thought

Finally, in substage six there is the beginning of symbolic thought. This is transitional to the pre operational stage of cognitive development. Babies can now form mental representations of objects.

This means that they have developed the ability to visualise things that are not physically present. This is crucial to the acquisition of object permanence – the most fundamental achievement of the whole sensorimotor stage of development.

Object Permanence

The main development during the sensorimotor stage is the understanding that objects exist and events occur in the world independently of one's own actions ('the object concept', or 'object permanence').

Object permanence means knowing that an object still exists, even if it is hidden. It requires the ability to form a mental representation (i.e. a schema) of the object.

For example, if you place a toy under a blanket, the child who has achieved object permanence knows it is there and can actively seek it. At the beginning of this stage the child behaves as if the toy had simply disappeared.

The attainment of object permanence generally signals the transition to the next stage of development (preoperational).

Blanket and Ball Study

Aim: Piaget (1963) wanted to investigate at what age children acquire object permanence.

Method: Piaget hid a toy under a blanket, while the child was watching, and observed whether or not the child searched for the hidden toy.

Searching for the hidden toy was evidence of object permanence. Piaget assumed that the child could only search for a hidden toy if s/he had a mental representation of it.

Results: Piaget found that infants searched for the hidden toy when they were around 8-months-old.

Conclusion: Children around 8 months have object permanence because they are able to form a mental representation of the object in their minds.

Evaluation:Piaget assumed the results of his study occur because the children under 8 months did not understand that the object still existed underneath the blanket (and therefore did not reach for it). However, there are alternative reasons why a child may not search for an object:

The child could become distracted or lose interest in the object and therefore lack the motivation to search for it, or simply may not have the physical coordination to carry out the motor movements necessary for the retrieval of the object (Mehler & Dupoux, 1994).

Critical Evaluation

There is evidence that object permanence occurs earlier than Piaget claimed. Bower and Wishart (1972) used a lab experiment to study infants aged between 1 – 4 months old.

Instead of using a Piaget’s blanket technique they waited for the infant to reach for an object, and then turned out the lights so that the object was no longer visible. They then filmed the infant using an infrared camera. They found that the infant continued to reach for the object for up to 90 seconds after it became invisible.

Again, just like Piaget's study there are also criticisms of Bower's 'reaching in the dark' findings. Each child had up to 3 minutes to complete the task and reach for the object. Within this time period, it is plausible they may have successfully completed the task by accident.

For example, randomly reaching out and finding the object or even reaching out due to the distress of the lights going out (rather than reaching out with the intention of searching for an object).

Violation of Expectation Research

A further challenge to Piaget’s claims comes from a series of studies designed by Renee Baillargeon. She used a technique that has come to be known as the violation of expectation (VOE) paradigm. It exploits the fact that infants tend to look for longer at things they have not encountered before.

In a VOE experiment, an infant is first introduced to a novel situation. They are repeatedly shown this stimulus until they indicate, by looking away, that it is no longer new to them. In Baillargeon et al’s (1985, 1987) study, the habituation stimulus was a ‘drawbridge’ that moved through 180 degrees.

violation of expectation task with possible and impossible events

The infants are then shown two new stimuli, each of which is a variation on the habituation stimulus. In Baillargeon’s experiments, one of these test stimuli is a possible event (i.e. one which could physically happen) and the other is an impossible event (i.e. one that could not physically happen in the way it appears).

In the ‘drawbridge’ study, a coloured box was placed in the path of the drawbridge. In the possible event, the drawbridge stopped at the point where its path would be blocked by the box. In the impossible event, the drawbridge appeared to pass through the box and ended up lying flat, the box apparently having disappeared.

Baillargeon found that infants spent much longer looking at the impossible event. She concluded that this indicated surprise on the infants’ part and that the infants were surprised because they had expectations about the behavior of physical objects that the impossible event had violated.

In other words, the infants knew that the box still existed behind the drawbridge and, furthermore, that they knew that one solid object cannot just pass through another. The infants in this study were five months old, an age at which Piaget would say that such knowledge is quite beyond them.


Baillargeon, R. (1987). Object permanence in 3½-and 4½-month-old infants. Developmental psychology, 23(5), 655.

Baillargeon, R., Spelke, E.S. & Wasserman, S. (1985). Object Permanence in Five-Month-Old Infants. Cognition, 20, 191-208.

Bower, T. G. R., & Wishart, J. G. (1972). The effects of motor skill on object permanence. Cognition, 1, 165–172.

Mehler, J., & Dupoux, E. (1994). What Infants Know: The New Cognitive Science of Early Development. Blackwell Publishers.

Piaget, J. (1952). The origins of intelligence in children. New York: International Universities Press.

Piaget, J. (1954). The construction of reality in the child (M. Cook, Trans.).

Piaget, J. (1964). Part I: Cognitive development in children: Piaget development and learning. Journal of research in science teaching, 2(3), 176-186.

Piaget, J. (1963). The Psychology of Intelligence. Totowa, New Jersey: Littlefield Adams.

How to reference this article:

McLeod, S. A. (2018). Sensorimotor stage. Retrieved from

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