Biological Approach in Psychology

Biological psychology, also called physiological psychology, is the study of the biology of behavior; it focuses on the nervous system, hormones and genetics. Biological psychology examines the relationship between mind and body, neural mechanisms, and the influence of heredity on behavior.

Key Features
• Natural Selection / Evolution
• Adaptation
• Scientific method
• Heredity
• Nomothetic (studies the group)
• Psychology should be seen as a science, to be studied in a scientific manner (usually in a laboratory).
• Thinking and behavior can be explained in terms of biological factors, e.g., genes & nervous system
• Human genes have evolved over millions of years to adapt behavior to the environment
• Patterns of behavior can be inherited. Therefore, most behavior will have an adaptive/evolutionary purpose
• Humans are similar to animals. Therefore, research can be carried out on animals as well as humans
• Follows a nomothetic approach as it focuses on establishing laws and theories about the effects of physiological and biochemical processes that apply to all people
• Lab Experiments
• Correlation studies
• Twin research
• Naturalistic observations
• Cross-cultural research
• Lab Experiments
• Correlation studies
• Twin research
• Naturalistic observations
• Cross-cultural research
• Electroencephalogram (EEG)
• Brain scans (CT, MRI, PET)
• Reductionist: ignores the environment and cognitive processes
• Deterministic – little room for free will
• Behaviourism – we are born a blank slate and not with instincts at birth
• The biological approach is determinist and views behavior as caused by biological factors over which we have no control

The biological approach believes behavior to be 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, feelings & 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.

Furthermore the biological approach argues that some of our behaviors and characteristics are passed on genetically because they enhance our survival such as attachment and memory.

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

Issues and Debates

Free will vs. determinism

It is strongly determinist as it views behavior as caused entirely by biological factors over which individuals have no control.

Nature vs. nurture

The biological approach is firmly on the nature side of the debate; however, it does recognize that our brain is a plastic organ that changes with experience in our social world, so it does not entirely deny the influence of nurture.

Cross-cultural research involves studying a particular behavior (e.g., gender, facial expressions) across different cultures. If the behavior is found to be similar across cultures, psychologists conclude that differences in behavior are biologically (i.e., nature) based.

However, if the behavior is found to be different across cultures, then it is likely to be affected by the environment (i.e., nurture).  Cross-cultural research is useful as it contributes to the nature-nurture debate in psychology.

Holism vs. reductionism

The biological approach is reductionist as it aims at explaining all behavior by the action of genetic or biochemical processes. It neglects the influence of factors such as early childhood experiences, conditioning, or cognitive processes.

Idiographic vs. nomothetic

The biological approach is nomothetic as it establishes laws and theories about the effects of physiological and biochemical processes that apply to all people.

Are the research methods used scientific?

The biological approach uses very scientific methods such as scans and biochemistry.  Animals are often used in this approach as the approach assumes that humans are physiologically similar to animals.

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 makeup, and fraternal twins have just 50 percent 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 that 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 twins raised apart have been criticized as the twins often share similar environments and are sometimes raised by a non-parental family member.

Methods of Studying the Brain

It is important to appreciate that the human brain is a highly 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.

Children begin to plan activities, make up games, and initiate activities with others. If given this opportunity, children develop a sense of initiative and feel secure in their ability to lead others and make decisions.

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 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.


The Voyage of the Beagle (1805 – 1836) – Darwin formulated his theory of natural selection by observing animals while traveling 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 were sold on 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 an evolutionary perspective to psychology.

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

Critical Evaluation

Charles Darwin proposed the theory of natural selection. He argued that genetically determined characteristics or behavior that enhance our chances of survival and reproduction would be passed on to the next generation and become more common in a population.

In contrast, traits that do not enhance survival will gradually disappear. Theories within the biological approach support nature over nurture. An example of behavior of evolutionary explanation is Bowlby’s theory of attachment.

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).

For example, 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.

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, replicated, and peer-reviewed.

A limitation is that most biological explanations are reductionist. They reduce behavior to the outcome of genes and other biological processes, neglecting the effects of childhood and our social and cultural environment. They don’t provide enough information to explain human behavior fully.

Furthermore, it could be argued that the biological abnormalities seen in mental disorders could be the result rather than the cause of the disorder as the brain is a plastic organ that changes with the way we use it, so it could be that, for example, the damage seen in the caudate nucleus is the result of anxiety rather than its cause.

Additionally, it could be argued that the unbalance in neurotransmitters such as low serotonin, in a depressed individual is the consequence rather than the cause of depression because the brain is a plastic organ that changes with the way we use it, so it could be that the depressed thinking causes the low level of serotonin observed.

It could be argued that twin studies do not separate nature and nature because twins are raised and live in the same environment and the difference in the concordance rate found between MZ and DZ twins could be due to the fact that MZ twins are treated more similarly by their parents than DZ twins because they look more similar.

Also, we usually do not find a 100% concordance rate in MZ twins for mental disorders, indicating that environmental and social factors must be involved in developing these disorders.

The biological approach is determinist as it sees our behavior as caused entirely by biological factors over which we have no control. This encourages people not to take responsibility for their actions and blame their genetic makeup.


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


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.

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