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Biological Psychology

published, updated 2015

The biological approach believes us to be as a consequence of our genetics and physiology. It is the only approach in psychology that examines thoughts, feelings, and behaviors from a biological and thus physical point of view.

Therefore, all that is psychological is first physiological. All thoughts, feeling & behavior ultimately have a biological cause. A biological perspective is relevant to the study of psychology in three ways:

1. Comparative method: different species of animal can be studied and compared. This can help in the search to understand human behavior.

2. Physiology: how the nervous system and hormones work, how the brain functions, how changes in structure and/or function can affect behavior. For example, we could ask how prescribed drugs to treat depression affect behavior through their interaction with the nervous system.

3. Investigation of inheritance: what an animal inherits from its parents, mechanisms of inheritance (genetics). For example, we might want to know whether high intelligence is inherited from one generation to the next.

Each of these biological aspects, the comparative, the physiological (i.e. the brain) and the genetic, can help explain human behavior.

Investigation of Inheritance

Twin studies provide geneticists with a kind of natural experiment in which the behavioral likeness of identical twins (whose genetic relatedness is 1.0) can be compared with the resemblance of dizygotic twins (whose genetic relatedness is 0.5).

In other words, if heredity (i.e. genetics) affects a given trait or behavior, then identical twins should show a greater similarity for that trait compared to fraternal (non-identical) twins.

There are two types of twins:

  • Monozygotic = identical twins (share 100% genetic information).

  • Dizygotic = non-identical twins (share 50% genetic information, similar to siblings).

Research using twin studies looks for the degree of concordance (or similarity) between identical and fraternal (i.e. non-identical) twins. Twins are concordant for a trait if both or neither of the twins exhibits the trait. Twins are said to be disconcordant for a trait if one shows it and the other does not.

Identical twins have the same genetic make-up, and fraternal twins have just 50 per cent of genes in common. Thus, if concordance rates (which can range from 0 to 100) are significantly higher for identical twins than for fraternal twins, then this is evidence that genetics play an important role in the expression of that particular behavior.

Bouchard and McGue (1981) conducted a review of 111 worldwide studies which compared the IQ of family members. The correlation figures below represent the average degree of similarity between the two people (the higher the similarity the more similar the IQ scores).

  • Identical twins raised together = .86 (correlation).

  • Identical twins raised apart = .72

  • Non-identical twins reared together = .60

  • Siblings reared together = .47

  • Siblings reared apart = .24

  • Cousins = .15

However, there are methodological flaws which reduce the validity of twin studies. For example, Bouchard and McGue included many poorly performed and biased studies in their meta-analysis. Also, studies comparing the behavior of twin raised apart have been criticized as the twins often share similar environments and are sometimes raised by non-parental family member.

Methods of Studying the Brain

It is important to appreciate that the human brain is an extremely complicated piece of biological machinery. Scientists have only just “scratched the surface” of understanding the many functions of the workings of the human brain. The brain can influence many types of behavior.

In addition to studying brain damaged patients we can find out about the working of the brain in three other ways.

1. Neuro Surgery

We know so little about the brain and its functions are so closely integrated that brain surgery is usually only attempted as a last resort. H.M. suffered such devastating epileptic fits that in the end a surgical technique that had never been used before was tried out.

This technique cured his epilepsy, but in the process the hippocampus had to be removed (this is part of the limbic system in the middle of the brain.) Afterwards H.M. was left with severe anterograde amnesia. I.e. He could remember what happened to him in his life up to when he had the operation but he couldn’t remember anything new. So now we know the hippocampus is involved in memory.

2. Electroencrphalograms (EEGs)

This is a way of recording the electrical activity of the brain (It doesn’t hurt and it isn’t dangerous!). Electrodes are attached to the scalp and brain waves can be traced. EEGs have been used to study sleep and it has been found that during a typical night’s sleep, we go through a series of stages marked by different patterns of brain wave.

One of these stages is known as REM sleep (Rapid Eye Movement sleep). During this our brain waves begin to resemble those of our waking state (though we are still fast asleep) and it seems that this is when we dream (whether we remember it or not).

3. Brain Scans

More recently methods of studying the brain have been developed using various types of scanning equipment hooked up to powerful computers. The CAT scan (Computerised Axial Tomography) is a moving X-ray beam which takes “pictures” from different angles around the head and can be used to build up a 3-dimensional image of which areas of the brain are damaged.

Even more sophisticated is the PET scan (Positron Emission Tomography) which uses a radioactive marker as a way of studying the brain at work. The procedure is based on the principle that the brain requires energy to function and that the regions more involved in the performance of a task will use up more energy. What the scan therefore enables researchers to do is to provide ongoing pictures of the brain as it engages in a mental activity.

These (and other) methods for producing images of brain structure and functioning have been extensively used to study language and PET scans in particular are producing evidence that suggests that the Wernicke-Gerschwind model may not after all be the answer to the question of how language is possible.

History of The Biological Approach

* The Voyage of the Beagle (1805 - 1836) - Darwin formulated his theory of natural selection through observing animals while travelling the world.

* Harlow (1848) Phineas Gage brain injury case study provides neuroscience with significant information regarding the working of the brain.

* Darwin (1859) publishes "On the Origin of Species by Means of Natural Selection". 1,250 copies were printed, most of which sold the first day.

* Jane Goodall (1957) began her study of primates in Africa, discovering that chimps have behaviors similar to all the human cultures on the planet.

* Edward Wilson (1975) published his book, "Sociobiology" which brought together evolutionary perspective to the psychology.

* The birth of Evolutionary Psychology begins with the publication of an essay "The Psychological Foundations of Culture" by Tooby and Cosmides (1992).

Biological Approach Summary

Key FeaturesMethodology
Basic AssumptionsAreas of Application
  • Psychology should be seen as a science, to be studied in a scientific manner (usually in a laboratory).
  • Behavior can be largely explained in terms of biology (e.g. genes/hormones).
  • Human genes have evolved over millions of years to adapt behavior to the environment. Therefore, most behavior will have an adaptive / evolutionary purpose.
  • Very Scientific
  • Highly application to other areas: Biology + Cog = Evolutionary Psy
  • Helped develop comparative psychology
  • Strong counter argument to the nurture side of the debate
  • Many empirical studies to support theories
  • Experiments – Low Ecological Validity
  • Humanism: too deterministic – little room for free-will
  • Doesn’t recognize cognitive processes
  • Reductionist
  • Bio psychological theories often over-simplify the huge complexity of physical systems and their interaction with the environment.

Critical Evaluation

Theories within the biological approach supports nature over nurture. However, it is limiting to describe behavior solely in terms of either nature or nurture, and attempts to do this underestimate the complexity of human behavior. It is more likely that behavior is due to an interaction between nature (biology) and nurture (environment).

A strength of the biological approach is that it provides clear predictions, for example, about the effects of neurotransmitters, or the behaviors of people who are genetically related. This means the explanations can be scientifically tested and ‘proven’.

A limitation is that most biological explanations are reductionist and don’t provide enough information to fully explain human behavior. Individuals may be predisposed to certain behaviors, but these behaviors may not be displayed unless they are triggered by factors in the environment. This is known as the ‘Diathesis Stress model’ of human behavior.


Bouchard, T. J., & McGue, M. (1981). Familial studies of intelligence: A review. Science, 212(4498), 1055-1059.

Darwin, C. (1859). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (1st ed.). London: John Murray.

Harlow, J. M. (1848). Passage of an iron rod through the head. Boston Medical and Surgical Journal, 39, 389–393.

Tooby, J., & Cosmides, L. (1992). The psychological foundations of culture. In J. Barkow, L. Cosmides, & J. Tooby (Eds.), The adapted mind: Evolutionary psychology and the generation of culture. New York: Oxford University Press.

Wilson, E. (1975). Sociobiology: The New Synthesis. Harvard University Press

How to reference this article:

McLeod, S. A. (2015). Biological psychology. Retrieved from

Further Information

Sex differences in the brain  pdf

What has neuroscience ever done for us?  pdf

Are Bigger Brains Better?  pdf

Listen to a MIT undergraduate lecture on Love and Evolution. Audio Broadcasts biological approach to psychology

BBC Radio 4: The influence of evolutionary theory, phrenology and a hole in Phineas Gage's head. Audio Broadcasts biological approach to psychology

BBC Radio 4: Dr Bunn discusses the impact of neurology on how we understand ourselves today. Audio Broadcasts biological approach to psychology

BBC Radio 4: Mind Myths. Audio Broadcasts biological approach to psychology

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