HL Extension: Animal research
- Animal models are used to gain insight into human physiology and behaviour.
- There are concerns when generalizing results of research from animal models to humans.
- There are ethical concerns about the use of animals in biopsychological research.
One of the most, if not the most, contentious issues in science is the use of animals in research. Psychologists use animals to gain greater insight into human behaviour and physiology because some research cannot be done with humans. Over the past few decades, we have seen major changes in the way that this research is carried out. In this chapter, we will look at the ethical considerations of animal research as well as the use of animal models to understand the role of the brain, hormones and genetics in human behaviour.
Around 29 million animals per year are currently used in experiments in the US and European Union countries. Rats and mice make up around 80% of the total. The good news is that the number of animals used in experiments has fallen by half in the past 30 years.
There are several reasons that we use animals to study human behaviour. First, procedures may be carried out – such as isolation and surgery – that would be unethical on humans.
In addition, the lifespan of an animal is significantly shorter than a human lifespan, so the effects of a variable – such as stress – can be studied over the course of a full lifetime and over several generations. In addition, the behaviour can be studied under controlled conditions in a way that would be impossible with humans.
For example, if we recall the study by Rogers & Kesner (2003), researchers were able to manipulate the levels of acetylcholine in order to see how this affected learning and memory. This effect was temporary, so it caused no long-term harm to the animal. In addition, the learning was highly controlled. This type of experiment would be very difficult to do on a human. However, the research allows us to generate a hypothesis about the role of acetylcholine in human beings. For example, modern research has shown depleted levels of acetylcholine in Alzheimer’s patients. As a result of animal research, today drugs are used in the treatment of Alzheimer’s disease – such as Aricept or Exelon- that attempt to stabilize acetylcholine levels. This can be seen as a justification for the research carried out on animals.
Animal models of behaviour are used when an animal has a similar behaviour or disease to what is seen in humans. This, however, can be problematic in some cases. For example, when looking at animal models of depression, it is not possible to measure the typical human symptoms such as loss of self-esteem, pessimism or suicidal thoughts. However, psychologists argue that they can study animals with a specific endophenotype – that is, genetic markers – which are related to certain behaviours associated with the depression. An animal model helps us to understand the biochemical and genetic factors that may lead to depression – or any other disorder or behaviour.
An endophenotype is the measurable biological, behavioural or cognitive markers that are found more often in individual organisms with a disease than in the general population.
In 2002, geneticists completed the mapping of the rat genome. Researchers found that rats and humans each have about 30.000 genes – only 300 are unique to either organism. That means that the genes of the two species are 99% similar. Much of the differences have to do with gene expression. Both humans and rats have a gene that is responsible for the development of a tail – but only in rats is this gene expressed.
Another example of an animal model in research was that used by LeDoux to understand what happens in the brain during the fear response. By using lesioning in rats, LeDoux (1996) determined that the amygdala played a key role in the fear response. He proposed a model based on his research with rats that argues that there are two paths in a fear response. When we see something fearful, the visual thalamus sends a message to the amygdala. This results in a fear response and blood pressure rises. This is a quick response that is important for our survival. He called this the low path. In the second path – the high path - the message from the thalamus passes through the visual cortex and the hippocampus and its meaning is interpreted. If the stimulus is perceived to not be a threat, the amygdala lowers blood pressure and ceases the fear reaction.
Current techniques for examining the human brain are still not able to study the neural systems in the way that animal models allow. Although researchers can study patients with brain lesions, these lesions often include damage to other structures and are not as precise as the animal models. In addition, because of the plastic nature of the brain, if the lesions occurred a long time again, the brain has changed in structure to compensate for the damage and so it is difficult to determine the exact effect of the lesion.
There are several criticisms of the use of animal models in the study of human behaviour. First, there is the question of external validity. Especially with regard to drug therapies, it is often the case that what is observed in animals does not predict what will happen in humans. It is questionable whether it is the physiology of the animal that leads to this lack of predictability, or whether it is a result of low ecological validity – that is, the highly controlled environment and the way that variables are operationalized.
External validity is the extent to which the results of a study can be generalized to other situations or, in the case of animal models, to people.
This leads us to the question the extent to which animal research can be generalized to humans. An animal model on its own cannot be generalized to humans. It is important that the researchers find evidence in humans that can be explained through the animal model. However, animal research might lead to inferences about human behaviour. This is called theoretical generalization.
Theoretical generalization is when the findings of a study contribute to the development of further theories.
A second criticism has to do with the quality of the data. Animals cannot readily communicate their responses, they can only be observed. This means that we cannot know the cognitive processes of the animal. This also means that research is open to researcher bias, where the researcher will see what is expected.
Finally, as you will see below, there are several ethical concerns about the use of animals. This will be discussed after we understand how research is done on animals.
Checking for understanding
Which of the following is not a justfication of animal research in psychology?
Animal research can be very expensive as animals must be cared for. There are clear ethical considerations that must be met. It is not true that if you use animals in your research, that you are now free from meeting ethical requirements.
What is a potential implication of the research done by Martinez & Kesner?
How do psychologists study mental illness in animals?
To what extent are rats genetically similar to humans?
Rats share 99% of the same genes that we have as humans; our differences are due to gene expression.
What term do psychologists use to describe the extent to which the results of animal research can be generalized to humans?
Which type of generalization allows us to make predictions about human behaviour based on what we see in animal models?
Theoretical generalization allows us to predict what might be true in humans, recognizing their differences. Representational generalization means that we can generalize outside of the sample to the larger population of the animal and inferential generalization means that the results can be generalized to other settings or situations. There is no such term as "external generalization."