Sample 2

The biological approach argues that human behaviour has physiological origins and that ‘biology’ should be taken into account when studying human beings. Psychologists use multiple research methods to investigate how environmental factors interact with biological systems in both animals and humans. Two research methods that are used in this approach are laboratory experiments and case studies.

The purpose of using laboratory experiments in the biological approach is for the researchers to establish a causal relationship between two variables - the independent and the dependent variable. Experiments are based on hypothesis testing - that is, making a measurable and testable hypothesis and then seeing if the results of the study are statistically significant so that they can reject the null hypothesis. In addition, an experiment must contain at least one group that receives a treatment (the manipulation of an independent variable), and a control group does not receive the treatment. In a true experiment, participants are randomly allocated to conditions.

Rogers & Kesner conducted a laboratory experiment with the aim to determine the role of a neurotransmitter acetylcholine in spatial memory formation; there are multiple acetylcholine receptors in the hippocampus that play a role in the consolidation of memory. Firstly, the researchers had mice run a simple maze to find food that was placed in one of the two corners. After having run the maze, but before memory could be consolidated, the mice were injected with one of two chemicals into their hippocampal region. The first group was injected with scopolamine, which blocks the acetylcholine receptors and thus inhibits the response. The second group was a control one, given a placebo injection of saline solution to make sure that getting an injection does not cause any change in memory. Thereafter, the two groups were placed again into the maze to see how long it would take them to find the food they had previously located. The results show that the scopolamine group took longer and made more mistakes in finding the food, whereas the control group learned faster and made fewer mistakes. All in all, the findings indicate that the neurotransmitter acetylcholine may play an important role in the consolidation of spatial memory and retrieval.

One of the most significant strengths of a laboratory experiment is that it has a highly standardized procedure so the study can be replicated by other researchers, and the reliability of the results can be further tested. Experiments also try to control extraneous variables and randomly allocate participants to conditions, which increases the internal validity, allowing for a cause and effect relationship to be established. On the other hand, they suffer from low ecological validity due to the highly controlled environments, meaning that the results may not reflect behaviour under normal conditions. It is also not always clear to what extent the results of animal research may be applicable to human beings such as from rats to humans in the Rogers & Kesner study.

Another research method in the biological approach is a case study. Case studies are comprehensive investigations of one individual with a particular brain abnormality or damage; case studies provide situations that cannot be ethically reproduced by researchers in a laboratory under controlled conditions. They are also often carried out longitudinally to observe short-term and long-term effects, where the same variables are investigated in repeated and different types of observations over long periods of time. An independent variable is not manipulated in this type of research and hence, no causal relationship can be established. In addition, psychologists study the brain-damaged patient by using triangulation - for example, more than one method, researcher, and different sources of data. 

Milner carried out a classic case study on HM on the role of the hippocampus in memory formation; HM sustained a serious head injury when he fell off his bicycle at the age of 7, and beginning from three years after his accident, suffered from repeating epileptic seizures. With the approval of HM and his family, tissue from the medial temporal lobe, including the hippocampus, was removed in an experimental surgery on both sides of his brain. Although HM remembered his childhood very well and his personality seemed relatively unchanged after the surgery, he had suffered from anterograde amnesia—not being able to transfer new information from short-term memory to long-term memory. Milner longitudinally studied HM through different methods such as psychometric testing, direct observations, interviews, MRI scans, and cognitive testing. The researchers have found that HM could not acquire new episodic memories [memories of autobiographical events] and semantic knowledge [general world knowledge], however, procedural memories were not impacted; they have concluded that hippocampal region plays a significant role in memory formation.

One of the strengths of case studies is that they collect rich data. Case studies collect data over a long period of time, accounting for both short-term and long-term effects on the patient’s behaviour; they also use a more holistic approach as opposed to experiments by looking at a range of behaviours, rather than measuring a single dependent variable. In addition, the use of method triangulation increases the validity of the results.  Nevertheless, generalizability is one of the most critical limitations of this type of research method; case studies often study brain abnormality or damage that is unique to an individual and for that reason, the observed results cannot be generalized to the behaviour of all human beings. In addition, a causal relationship cannot be established as an independent variable is not manipulated in this type of research. Lastly, it might also be difficult for the researcher to acquire and verify information about the patient prior to his/her accident, which may otherwise be of some use when drawing conclusions.

While laboratory experiments may be helpful for researchers to determine cause and effect relationships that can be tested for reliability through replication by other researchers, case studies may provide more unique and in-depth research into individual human behaviour that could not be otherwise ethically reproduced. All in all, despite some of the methods' weaknesses, psychologists generally attempt to use them together to investigate human beings in terms of the roots of physical processes and physiological origins.