Learning Outcome Essay: Outline two principles that define the biological level of analysis.

Outline two principles that define the biological level of analysis.

The biological level of analysis argues that there are physiological origins of behaviour and that human beings should be studied as biological systems. This means that we should also consider how the environment and cognition may interact with biological systems and affect physiology, as this is a bidirectional relationship. A bidirectional relationship simply means that two things can affect each other, such as biology can affect cognition and cognition can affect biology. There are multiple principles that define the biological of analysis, which means that these create the basis for the theories within this area of analysis, and two of them are patterns of behaviour can be inherited and non-human animal research can inform understanding of human behaviour.

The first principle is patterns of behaviour can be inherited. This means that human behaviours, cognitions, and emotions can to some extent be explained through genetic inheritance and evolutionary adaptations. Studies that explore this principle are usually correlational studies which is able to suggest if there is a relationship between two principles. One of these studies is the study made by Bouchard et al. in 1990, which is often referred to as ‘The Minnesota Twin Study’. The aim of this study was to investigate the relative influence of environment and genetic factors on human characteristics and behaviours, focusing on among others, intelligence. This was a cross-cultural correlational study of more than 100 pairs of reared-apart twins and siblings whose data was compared with twins and siblings reared together. The participants were identical twins (monozygotic/MZ) and non-identical twins (dizygotic/DZ), with an average age of 41 years. Each participant underwent over 50 hours of psychological testing and interviews. In twin research, the correlation found between each twin and therefore presumably between genetic inheritance and a particular behaviour is called the concordance rate. The concordance rates for IQ were:

MZ twins reared together: 86% (0.86)

MZ twins reared apart: 76% (0.76)

DZ twins reared together: 55% (0.55)

Biological siblings reared together: 47% (0.47)

Bouchard et al concluded that about 70% of intelligence is heritable, meaning that genes account for 70% of the variation in intelligence from one person to the next. This study shows that patterns of behaviour can be inherited, as the concordance rate for the IQ of MZ twins was far higher than for DZ twins or siblings. Therefore a large part of this behaviour is genetically based and thus inherited.

The second principle is that non-human animal research can inform understanding of human behaviour. Animal research is often used when there are ethical boundaries on humans so that they cannot be used in studies. There are less ethical limitations on animal testing than humans, and since humans and animals share a, to some extent, similar biological makeup, some results from animal research can be generalized to humans. One study that used animals in their research was the study by Martinez and Kesner in 1991. The aim of this study was to investigate the role of acetylcholine on memory encoding and memory retrieval. This was a laboratory experiment using rats. The rats were trained to learn a simple maze, but before the memories could be learned well-enough to be transferred from the short-term memory to the long-term memory, the rats were divided into three groups and injected with drugs.

Group one was injected with scopolamine, which is known to block the reception of acetylcholine by the post-synaptic neurons. This means that acetylcholine, a neurotransmitter expected to help form memories, cannot travel from one neuron to another. This was the no acetylcholine condition.

Group two was injected with physostigmine, a drug that blocks cholinesterase, which is what cleans up the acetylcholine from the receptor proteins on the post-synaptic neurons, returning the neurons to their resting potential, where no nerve impulse is being sent. Therefore the acetylcholine continued to act. This was the high acetylcholine condition.

Group three was the placebo group, and was injected with an inert saline solution that had no effect on acetylcholine. This was the control condition.

Rats were then placed back in the maze and ran multiple trials over two days. Their learning and memory was measured by comparing the number of mistakes they made while completing the maze. The difference between the first five and last five trials on day one was taken as a measurement of encoding, while the difference between the last five trials on day one and the first five trials on day two was used to measure retrieval. The no acetylcholine condition showed a deficit in encoding (but not retrieval), making relatively more mistakes during the last five trials on the first day. The high acetylcholine condition made relatively fewer mistakes during the last five trials on the first day and showed no deficit in encoding. However, the high acetylcholine condition did show a deficit in retrieval.

This suggest that acetylcholine plays an important role in memory encoding, because the rats with low acetylcholine levels wandered around the maze as though lost, even though they had learned it previously. At the same time, while acetylcholine may be necessary for memory encoding, the physostigmine condition suggests that too much acetylcholine may interfere with memory encoding and retrieval.

It is clear that these principles guide studies from a biological perspective.