2.1 Outline principles that define the biological level of analysis and explain how these principles may be demonstrated in research

2.1 Outline principles that define the biological level of analysis and explain how these principles may be demonstrated in research

Principle 1: There are biological correlates of behaviour.

This means that there are physiological origins of behaviour such as neurotransmitters, hormones, specialized brain areas, and genes. The biological level of analysis is based on reductionism, which is the attempt to explain complex behaviour in terms of simple causes.

Newcomer et al. (1999)

Aim: To investigate whether high levels of the stress hormone cortisol interfere with verbal declarative memory.

Method: It was a laboratory experiment. Participants were split into three groups.

Group 1 (high dose cortisol) had tablets containing 160 mg of cortisol for four days.

Group 2 (low dose cortisol) had tablets with 40 mg of cortisol for four days.

Group 3 (control) had placebo tablets.

Participants listened to a prose paragraph and had to recall it as a test of verbal declarative memory.

Results: The results showed that group 1 performed the worst on the memory test compared to group 2 and 3.

Conclusion: The experiment shows that an increase in cortisol over a period has a negative effect on memory.

Principle 2: Animal research can provide insight into human behaviour.

This means that researchers use animals to study physiological processes because it is assumed that most biological processes in non-human animals are the same as in humans. One important reason for using animals is that there is a lot of research where humans cannot be used for ethical reasons.

Rosenzweig and Bennet (1972)

Aim: To investigate whether environmental factors such as a rich or an impoverished environment would affect the development of neurons in the cerebral cortex.

Method: It was a series of laboratory experiments. The participants were rats.

Group 1 was placed in an enriched environment with lots of toys.

Group 2 was placed in a deprived environment with no toys.

The rats spent 30 or 60 days in their respective environments before being killed.

Results: The brain of the rats in group 1 showed a thicker layer of neurons in the cortex compared to the deprived group.

Conclusion: The study shows that the brain grows more neurons if stimulated.

Principle 3: Human behaviour is, to some extent, genetically based.

The means that behaviour can, to some extent, be explained by genetic inheritance, although this is rarely the full explanation since genetic inheritance should be seen as genetic predisposition which can be affected by environmental factors.

Researchers interested in the genetic origin of behaviour often use twins so that they can compare one twin with the other on a variable such as intelligence, depression or anorexia nervosa. Identical twins (monozygotic twins - MZ) are 100% genetically identical as they have developed from the same egg. They therefore act as a control for each other. Fraternal twins (dizygotic twins - DZ) have developed from two different eggs. They share around 50% of their genes so they are no more similar than siblings. Twin research never shows a 100% concordance rate so it is believed that genes are a predisposing factor rather than the cause of behaviour. Therefore it is also important to consider what environmental factors could influence the expression of the genetic predisposition.

Bouchard et al (1990)

Aim: To investigate the relative influence of environment and genetic factors on human characteristics and behaviours, including intelligence.

Method: The participants were MZ reared apart (MZA) and MZ reared together (MZT). Each participant underwent over 50 hours of psychological testing and interviews.

Results: The researchers found that MZT had a concordance rate of IQ of 86% compared to MZA with a concordance rate of IQ of 76%.

Conclusion: This study shows a link between genetic inheritance and intelligence but it does not rule out the role of the environment.