Reductionism in Psychology: Definition and Examples

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.

What is Reductionism?

Reductionism is based on the scientific assumption of parsimony – that complex phenomenon 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 can identify a cause and an effect (i.e., Reductionism is a form of determinism).

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

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



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 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.


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 and Wernicke’s area (but holism could state: the influence of family, education, and social class on language). Another example of biological reductionism is aggression – e.g., testosterone levels.


Structuralism was one of the first approaches in psychology. Wundt tried to break conscious experiences down into their constituent (i.e., basic) parts: images, sensations, and feelings.

Cognitive psychology

Cognitive psychology uses the principle of machine reductionism as a means to describe and explain behavior.

Psychodynamic approach

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).

More recent computer innovations, such as the Internet and connectionist networks, can be described as holistic 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 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 into 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 of 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 to 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 into 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.

Olivia Guy-Evans

BSc (Hons), Psychology, MSc, Psychology of Education

Associate Editor for Simply Psychology

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

Saul Mcleod, PhD

Educator, Researcher

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.