Biological Approach- Assumptions

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Assumption 1: Evolutionary influences

To evolve means to change with time. In Psychology, the theory of evolution has been used to explain how the human mind and behaviour have changed over millions of years so that they are adapted to the demands of our individual environments.

 The notion of adaptiveness is based on Darwin’s theory of natural selection. This is the idea that any genetically determined behaviour that enhances an individual’s chance of survival and reproduction will be naturally selected (the genes will be passed onto the next generation). An example of this is altruistic behaviour where parents risk their lives to save their offspring. The theory of natural selection would say that altruism is an inherited, adaptive trait because saving an offspring enhances the survival of that individual’s gene pool. 

One of the key concepts of the evolutionary approach is the environment of evolutionary adaptiveness (EEA). This is the environment to which any species is adapted and the selective pressures that existed at that time. Evolutionary psychologists do not assume that all forms of behaviour are adaptive – only the ones that ensure survival. Example:

EEA can explain why humans have such large brains relative to their body size. This theory would propose that the human brain has evolved in response to the complex social organisation of our species.

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Assumption 2: Localisation of brain function

Localisation of brain function refers to the principle that certain areas of the brain are responsible for different functions. The cerebral cortex covers the surface of the brain. This is the region of the brain responsible for higher order cognitive functions.The cerebral cortex is divided into four lobes. The most important is the frontal cortex or lobe which is involved in creativity and thinking. Other lobes include the occipital lobe, which is associated with vision. The parietal lobes receive sensory information such as temperature, touch and pain. The temporal lobes are responsible for much of our memory processing as well as the processing of auditory information.


Maguire et al (2000) used MRI scans to demonstrate that taxi drivers have larger hippocampi than non-taxi drivers, supporting the view that the hippocampus is important in spatial memories.

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Assumption 3: Neurotransmitters

A neurotransmitter is a chemical substance that is released at the junctions between neurons within the brain. One neuron communicates with another neuron at a synapse, where the message is relayed by chemical messengers (neurotransmitters). Neurochemical changes affect the transmission of messages in the nervous system and, according to the biological assumption, control physiological and psychological behaviour.


The neurotransmitter serotonin can have a variety of effects on our behaviour. Serotonin plays a role in our mood, sleep and appetite. If serotonin is at an optimum level, this will make us feel happy, however, if it is too high we may feel anxious and stressed and if it is too low we may feel depressed.High levels of the neurotransmitter dopamine have been associated with schizophrenia. This is supported by the fact that drugs that block dopamine activity reduce schizophrenic symptoms.

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