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What Is Reductionism?

What Is Reductionism?

How psychologists use reductionism to understand behavior

By Saul McLeod, updated


Reductionism is the belief that human behavior can be explained by breaking it down into smaller component parts.

Reductionists say that the best way to understand why we behave as we do is to look closely at the very simplest parts that make up our systems, and use the simplest explanations to understand how they work.

Reductionism is based on the scientific assumption of parsimony - that complex phenomena should be explained by the simplest underlying principles possible. Strong supporters of reductionism believe that behavior and mental processes should be explained within the framework of basic sciences (e.g. physiology, chemistry.... ).

However any explanation of behavior at its simplest level can be deemed reductionist. The experimental and laboratory approach in various areas of psychology (e.g. behaviorism, biological, cognitive) reflects a reductionist position.

This approach inevitably must reduce a complex behavior to a simple set of variables that offer the possibility of identifying a cause and an effect (i.e. Reductionism is a form of determinism).

Reductionism works at different levels. The lowest level of reductionism offers physiological explanation: these attempt to explain behavior in terms of neurochemical, genes and brain structure.

At the highest sociocultural level, explanations focus on the influence on behavior of where and how we live. Between these extremes there are behavioral, cognitive and social explanations.

Examples of Reductionism in Psychology

  • Behaviorism uses a very reductionist vocabulary: stimulus, response, reinforcement, and punishment. These concepts alone are used to explain all behavior.

    This is called environmental reductionism because it explains behavior in terms of simple simple building blocks of S-R (stimulus-response) and that complex behavior is a series of S-R chains. Behaviorists reduce the concept of the mind to behavioral components, i.e., stimulus-response links.

  • Biopsychology - Explanations for the cause of mental illnesses are often reductionist. Genetics, and neurochemical imbalances are frequently highlighted, as being the main cause of these disorders. In the case of schizophrenia for example excess production of the neurotransmitter dopamine is seen as a possible cause.

    This view clearly has implications for treatment. Gender can also be reduced to biological factors (e.g. hormones). Also, language can be reduced to structures in the brain, e.g. Broca’s area, Wernicke’s area (but holism could state: influence of family, education, social class on language). Another example of biological reductionism is aggression – e.g. testosterone levels.

  • Structuralism – One of the first approaches in psychology. Wundt tried to break conscious experiences down into its constituent (i.e. basic) parts: images, sensations and feelings.
  • Cognitive psychology uses the principle of machine reductionism as a means to describe and explain behavior.

    More recent computer innovations, such as the Internet and connectionist networks can be described as holist because the network behaves differently from the individual parts that go to make it up. The whole appears to be greater than the sum of its parts.

  • The psychodynamic approach is reductionist in so far as it relies on a basic set of structures that attempt to simplify a very complex picture (e.g. id, ego, superego, unconscious mind).


The use of a reductionist approach to behavior can be a useful one in allowing scientific study to be carried out. Scientific study requires the isolation of variables to make it possible to identify the causes of behavior.

Breaking complicated behaviors down to small parts means that they can be scientifically tested. Then, over time, explanations based on scientific evidence will emerge.

For example, research into the genetic basis on mental disorders has enabled researchers to identify specific genes believed to be responsible for schizophrenia.

This way a reductionist approach enables the scientific causes of behavior to be identified and advances the possibility of scientific study.

A reductionist approach to studying mental disorders has led to the development of effective chemical treatments

However, some would argue that the reductionist view lacks validity.

For instance, we can see how the brain responds to particular musical sounds by viewing it in a scanner, but how you feel when you hear certain pieces of music is not something a scanner can ever reveal.

Just because a part of the brain that is connected with fear is activated while listening to a piece of music does not necessarily mean that you feel afraid.

In this case, being reductionist is not a valid way of measuring feelings. 


It can be argued that reductionist approaches do not allow us to identify why behaviors happen. 

For example, they can explain that running away from a large dog was made possible by our fear centers causing a stress response to better allow us to run fast, but the same reductionist view cannot say why we were afraid of the dog in the first place. 

In effect, by being reductionist we may be asking smaller, more specific questions and therefore not addressing the bigger issue of why we behave as we do.

It has been suggested that the usefulness of reductionist approaches depends on the purpose to which they are put.

For example, investigating brain response to faces might reveal much about how we recognize faces, but this level of description should not perhaps be used to explain human attraction. 

Likewise, whilst we need to understand the biology of mental disorders, we may not fully understand the disorder without taking account of social factors which influence it.

Thus, whilst reductionism is useful, it can lead to incomplete explanations.

Interactionism is an alternative approach to reductionism, focusing on how different levels of analysis interact with one another.

It differs from reductionism since an interactionism approach would not try to understand behavior from explanations at one level, but as an interaction between different levels.

So for example, we might better understand a mental disorder such as depression by bringing together explanations from physiological, cognitive and sociocultural levels.

Such an approach might usefully explain the success of drug therapies in treating the disorder; why people with depression think differently about themselves and the world; and why depression occurs more frequently in particular populations.

How to reference this article:

McLeod, S. A. (2020). What is reductionism. Simply Psychology.

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