Assimilation vs accommodation: what Piaget actually meant, and why you never get one without the other

In Jean Piaget's theory, assimilation and accommodation are the two sides of adaptation to the environment. In assimilation, you fit something new into a schema that you already have. The schema does not have to change. In accommodation, the schema changes so that it fits the particular features of the new thing. Piaget called the balance between the two adaptation, and the process that produces this balance equilibration. He described the pair in 1936, in his book "La naissance de l'intelligence chez l'enfant".

A common explanation makes the two terms sound like two steps: first assimilation, then accommodation when assimilation fails. Piaget did not see it that way. For him, both processes are present in every act. This article gives you the definitions in Piaget's own words and one question that sorts exam examples. It also shows the observations of his son that Piaget used to explain the terms in 1936.

• Assimilation: you interpret the new thing so that it fits a schema that you already have.
• Accommodation: the schema changes so that it fits the new thing.
• Piaget built both terms on a model from biology. For him, intelligence was a special case of biological adaptation.
• In Piaget's view, there is no pure assimilation. Every assimilation contains some accommodation, and every accommodation needs assimilation.
• When assimilation dominates, the result is play. When accommodation dominates, the result is imitation. Piaget described this in 1945.

The difference in one table

The two columns do not describe two separate events. They describe two sides of one process. In 1937, Piaget called assimilation and accommodation "the two poles of an interaction between the organism and the environment". For Piaget, this interaction is the condition for all biological and intellectual functioning. We translated all quotations from Piaget's French originals ourselves.

The one question that sorts any example

Exam questions usually describe a situation and ask which process it shows. To answer, use these steps.

1. 1.Find the schema: the existing way of acting or thinking that the person uses.
2. 2.Find the new thing: the object, event or information that the person meets.
3. 3.Ask: did the schema have to change so that the new thing fits?
4. 4.If the answer is no, assimilation dominates. If the answer is yes, accommodation dominates.

The word "dominates" is important. In Piaget's view, every example contains both processes. The question only shows which side you can see in the situation. The examples below are teaching examples, not studies. Only the examples with Laurent come from Piaget's observations.

Watch for one common misconception in exams: accommodation does not only mean that a new schema forms. The APA Dictionary of Psychology defines accommodation as the process "in which already existing structures are changed to accommodate new information". The German Dorsch lexicon of psychology adds that accommodation can also split an existing schema into more specialised ones, or create new links between schemas.

Where the terms come from: Piaget's biology

Piaget thought in biological terms. The introduction of his 1936 book has the title "Le problème biologique de l'intelligence", the biological problem of intelligence. There, Piaget writes that "intelligence is an adaptation", and that it is a special case of biological adaptation. An organism takes elements of its environment into its own cycle of processes, and it keeps its own organisation while it does so. Piaget calls this relation assimilation. He also writes that biological assimilation is the starting point of the elementary forms of mental assimilation. The Dorsch lexicon also records that Piaget borrowed the term from biology.

When the environment changes, there are two possibilities. Either the cycle breaks, or the cycle changes and stays closed. Piaget writes: "If we call this result of the pressures exerted by the environment accommodation, we can say that adaptation is an equilibrium between assimilation and accommodation."

The same is true for intelligence. Intelligence assimilates when it fits all experience into its own frameworks. It accommodates when it adjusts these frameworks to experience. Next to adaptation, Piaget names a second basic function: organisation. For Piaget, organisation is the internal side of the cycle, and adaptation is its external side. Both functions stay the same at all ages. Between the child and the adult, Piaget writes, the structures change continuously, but "the main functions of thought remain constant".

What Piaget saw in his son Laurent

Piaget did not take his evidence for the two processes from a laboratory. He observed his own children, among them his son Laurent and his daughter Lucienne. The first chapter of the 1936 book describes the sucking reflex in the first weeks of life. Piaget wrote ages as years, months and days: 0;0(9) means nine days.

• Lucienne sucked her hand a quarter of an hour after birth, and Laurent sucked his hand half an hour after birth.
• On the day after his birth, Laurent took the nipple with his lips. Nobody had to hold it in his mouth.
• At 0;0(9), Laurent looked for the breast. He sucked a down quilt and then a wool blanket. Each time, he let go after a moment and started to cry again.
• Piaget offered his bent index finger to Laurent, who cried with hunger. Laurent sucked it, let go after a few seconds and cried. The second try gave the same result. On the third try, he sucked for a long time.

From these scenes, Piaget identifies three forms of assimilation. Reproductive assimilation is repetition: the reflex becomes stronger because the child uses it. Generalising assimilation takes more and more objects into the sucking schema. In the first two weeks, the child sucks its own fingers, fingers that someone offers, the pillow and the quilt. Recognitive assimilation is a first, practical recognition: a very hungry child tells the nipple apart from everything else. The Dorsch lexicon lists a fourth form, reciprocal assimilation, in which different schemas are coordinated with each other.

Accommodation is also present in the reflex. Piaget points to Laurent's earlier contact with the nipple and his experience of the milk. Without this experience, Piaget writes, Laurent would probably not have rejected the quilt, the wool and the finger so quickly. So the sucking depends on experience. Piaget adds that this accommodation is inseparable from a gradual assimilation. The schema then continues to grow. By the end of the second month, Piaget writes, the child sucks his thumb systematically. At about five months, his hands bring all objects to his mouth.

Why there is never only assimilation

A common explanation describes a sequence. The child assimilates as long as possible, and accommodation starts only when assimilation fails. Piaget described it differently. In his 1936 introduction, he writes: "Assimilation can never be pure, because by incorporating new elements into earlier schemas, intelligence constantly modifies them to adjust them to the new data." The reverse is also true. Things are never known "in themselves", because accommodation is only possible through the opposite process of assimilation.

In 1975, Piaget made this idea a basic assumption of his book on equilibration. His second postulate says: "Every assimilation schema must accommodate itself to the elements that it assimilates". So the schema changes according to the particular features of the new thing. But it does not lose its continuity or its earlier power to assimilate.

The study-guide rule is not completely wrong. In 1937, Piaget also wrote that assimilation requires a continuous accommodation of the schemas, but that it resists every new accommodation. A schema keeps its form as long as the new thing fits approximately. The Dorsch lexicon also says that accommodation occurs when the differences become too large, or when assimilation fails because the new thing does not fit. So the rule describes the case that you can see: a large, new accommodation. The small accommodation in every act stays invisible.

For an exam, this means: do not write that assimilation and accommodation are separate phases. Write that the two always work together, and that one side or the other dominates in a given situation.

Equilibration: how the two stay in balance

Equilibration is Piaget's name for the process that brings assimilation and accommodation into balance. Piaget describes it in 1964, in "Six études de psychologie". New events in the world or in the body put action out of balance. Hunger starts the search for food, and an object that you meet can raise a question. In Piaget's words, every new behaviour does not only restore the balance. It also tends "towards an equilibrium more stable than that of the state before this disturbance".

In 1975, Piaget wrote a whole book about equilibration. In its foreword, he speaks of "majorante" equilibrations: equilibrations that correct and complete earlier forms of balance. In the first chapter, he writes that the real source of progress is not a return to the earlier form of balance, but an improvement of it. Disequilibrium only has the role of a trigger.

Do not confuse equilibration with organisation. For Piaget, organisation is the internal side of the cycle of schemas. Equilibration is the process that balances assimilation and accommodation.

When one side dominates: play and imitation

In his 1945 book "La formation du symbole chez l'enfant", Piaget uses the pair to explain two more types of behaviour. In the introduction, he writes that the primacy of accommodation marks imitation, and the primacy of assimilation explains play. The part on play says: "Play is essentially assimilation, or assimilation that takes priority over accommodation."

The examples in the table are teaching examples. Piaget gives an early example of his own: a baby sucks the thumb instead of the breast. Here the thumb takes the place of the breast, and assimilation dominates. But Piaget says clearly that the thumb is not a substitute every time a baby sucks it. At the end of the book, he sums up: as long as there is disequilibrium, one of the two sides dominates. When accommodation dominates, the result is representative imitation. When assimilation dominates, the result is symbolic play. When the two move towards balance, the result is cognitive representation.

Same words, other theories: coping and trauma therapy

If you read "assimilative" or "accommodative" in a text about stress, ageing or trauma, a different model can be meant. Here are two examples.

Jochen Brandtstädter and Gerolf Renner use the words for two ways of coping with crises. Their 1990 study describes two modes of coping that complement each other:

• Assimilative: you change your circumstances so that they fit your personal preferences. The scale for this mode is called Tenacious Goal Pursuit.
• Accommodative: you adjust your preferences to the limits of the situation. The scale for this mode is called Flexible Goal Adjustment.

In the study, both scales predicted high life satisfaction and low depression. In a cross-sectional sample of 890 people aged 34 to 63, coping shifted gradually from the assimilative mode to the accommodative mode with age.

Cognitive processing therapy (CPT), a treatment for post-traumatic stress disorder, uses the words for thoughts about a trauma. A 2009 study by Ana Sobel, Patricia Resick and Aline Rabalais coded written statements by 37 women who had survived rape. The women wrote the statements before and after CPT. The study treated assimilated and overaccommodated thoughts as problematic, and accommodated thoughts as realistic. After the therapy, the accommodated statements increased, and the assimilated and overaccommodated statements decreased.

Both models use the same logic as Piaget's pair: either the world is fitted to the person, or the person is fitted to the world. But each one is a separate theory. In an exam about Piaget, neither model belongs in the definition.

What the criticism and later research say

Piaget's terms are influential, but they are not undisputed. In 1982, Jack Block published an essay in the journal Child Development. According to the abstract of Block's essay, the essay "specifies some problems in the Piagetian characterizations of assimilation and accommodation". Block proposes a "revised and restricted" version in which the two are "separable adaptive strategies". For Piaget, the two are inseparable. Block also argues that equilibration expresses an orientation to limit anxiety: people keep or build an understanding of the world that is not disconfirmed.

In 1996, Orlando Lourenço and Armando Machado replied in Psychological Review to ten common criticisms of Piaget's theory. According to the abstract of their reply, most of the criticisms come from misinterpretations of Piaget's work, and many ignore the changes that Piaget made after 1970. But the authors do not claim that the problems of the theory vanish when it is better understood.

The terms are still in use. A 2022 systematic review in European Psychologist analysed 473 psychology articles from 1998 to 2018 that use assimilation and accommodation. It sorted them into ten categories. The authors found a common understanding of the pair, with the work of Baldwin and Piaget "influencing practically all views". They also asked future research to state the direction of the adaptation explicitly. One of the open questions that they name is the interdependence and synchronicity of the two processes.

So Block's objection is about how the two terms are defined: he wants to separate them, and Piaget does not. If an exam asks for a criticism of the terms, Block is the matching example.

How to keep the two terms apart

The general meanings of the two words help. The APA Dictionary gives the general meaning of assimilation as "absorbing, incorporating, or making similar", and of accommodation as "adjustment or modification".

• Assimilation: the new thing is made similar to what you know. The schema stays as it is.
• Accommodation: you make an adjustment. The schema changes.

When you learn the two terms, you go through both processes yourself. First, you fit the terms into what you already know. Then you change what you know until the difference is clear. Our guide to memorising psychology terminology explains which study methods help you remember more.

Psychology World is a dictionary app with more than 18,000 psychology terms, and it supports this type of practice. Search the dictionary, and save the terms that you find to one bookmark list, for example "Piaget". Then study the list as flashcards, as multiple-choice questions, or type each answer. The multiple-choice mode needs a list with a minimum of four terms. A daily-word notification also brings a new term to you. The home page shows the four steps of the learning loop and what each study mode does.