Biological Approach Psychology Twin Studies
Walberto Kennedy
Biological psychology, also called physiological psychology, is the study of the biology of behavior; it focuses on the nervous system, hormones and genetics. Biological psychology examines the relationship between mind and body, neural mechanisms, and the influence of heredity on behavior.
The biological approach believes behavior to be a consequence of our genetics and physiology. It is the only approach in psychology that examines thoughts, feelings, and behaviors from a biological and, thus physical point of view.
Therefore, all that is psychological is first physiological. All thoughts, feelings & behavior ultimately have a biological cause. A biological perspective is relevant to the study of psychology in three ways:
2. Physiology : how the nervous system and hormones work, how the brain functions, how changes in structure and/or function can affect behavior. For example, we could ask how prescribed drugs to treat depression affect behavior through their interaction with the nervous system.
3. Investigation of inheritance: what an animal inherits from its parents, mechanisms of inheritance (genetics). For example, we might want to know whether high intelligence is inherited from one generation to the next.
The biological approach is firmly on the nature side of the debate; however, it does recognize that our brain is a plastic organ that changes with experience in our social world, so it does not entirely deny the influence of nurture.
Cross-cultural research involves studying a particular behavior (e.g., gender, facial expressions) across different cultures. If the behavior is found to be similar across cultures, psychologists conclude that differences in behavior are biologically (i.e., nature) based.
However, if the behavior is found to be different across cultures, then it is likely to be affected by the environment (i.e., nurture). Cross-cultural research is useful as it contributes to the nature-nurture debate in psychology.
The biological approach uses very scientific methods such as scans and biochemistry. Animals are often used in this approach as the approach assumes that humans are physiologically similar to animals.
Twin studies provide geneticists with a kind of natural experiment in which the behavioral likeness of identical twins (whose genetic relatedness is 1.0) can be compared with the resemblance of dizygotic twins (whose genetic relatedness is 0.5).
Research using twin studies looks for the degree of concordance (or similarity) between identical and fraternal (i.e., non-identical) twins. Twins are concordant for a trait if both or neither of the twins exhibits the trait. Twins are said to be disconcordant for a trait if one shows it and the other does not.
Thus, if concordance rates (which can range from 0 to 100) are significantly higher for identical twins than for fraternal twins, then this is evidence that genetics play an important role in the expression of that particular behavior.
Bouchard and McGue (1981) conducted a review of 111 worldwide studies which compared the IQ of family members. The correlation figures below represent the average degree of similarity between the two people (the higher the similarity, the more similar the IQ scores).
Children begin to plan activities, make up games, and initiate activities with others. If given this opportunity, children develop a sense of initiative and feel secure in their ability to lead others and make decisions.
One of these stages is known as REM sleep (Rapid Eye Movement sleep). During this, our brain waves begin to resemble those of our waking state (though we are still fast asleep) and it seems that this is when we dream (whether we remember it or not).
The procedure is based on the principle that the brain requires energy to function and that the regions more involved in the performance of a task will use up more energy. What the scan, therefore, enables researchers to do is to provide ongoing pictures of the brain as it engages in mental activity.
These (and other) methods for producing images of brain structure and functioning have been extensively used to study language and PET scans, in particular, are producing evidence that suggests that the Wernicke-Gerschwind model may not after all be the answer to the question of how language is possible.
Charles Darwin proposed the theory of natural selection. He argued that genetically determined characteristics or behaviors that enhance our chances of survival and reproduction would be passed on to the next generation and become more common in a population.
However, describing behavior solely in terms of either nature or nurture is limiting, and attempts to do this underestimate the complexity of human behavior. It is more likely that behavior is due to an interaction between nature (biology) and nurture (environment).
For example, individuals may be predisposed to certain behaviors, but these behaviors may not be displayed unless they are triggered by factors in the environment. This is known as the diathesis-stress model of human behavior.
A strength of the biological approach is that it provides clear predictions, for example, about the effects of neurotransmitters or the behaviors of people who are genetically related. This means the explanations can be scientifically tested, replicated, and peer-reviewed.
Furthermore, it could be argued that the biological abnormalities seen in mental disorders could be the result rather than the cause of the disorder as the brain is a plastic organ that changes with the way we use it, so it could be that, for example, the damage seen in the caudate nucleus is the result of anxiety rather than its cause.
Additionally, it could be argued that the unbalance in neurotransmitters such as low serotonin, in a depressed individual is the consequence rather than the cause of depression because the brain is a plastic organ that changes with the way we use it, so it could be that the depressed thinking causes the low level of serotonin observed.
It could be argued that twin studies do not separate nature and nature because twins are raised and live in the same environment, and the difference in the concordance rate found between MZ and DZ twins could be due to the fact that MZ twins are treated more similarly by their parents than DZ twins because they look more similar.
The biological approach is determinist as it sees our behavior as caused entirely by biological factors over which we have no control. This encourages people not to take responsibility for their actions and blame their genetic makeup.
The genotype describes the genetic configuration of an individual, whereas phenotype describes the combined effects of genetic makeup and surrounding environment on behaviour. The nature-nurture debate highlights a key argument in psychology, over the relative influence of biology and environment on the characteristics of an individual; an extreme biological approach assumes that these are determined solely by nature.
Interactions between regions of the brain help to control different functions, which biological psychologists assume to be significant in determining our actions. For instance, the occipital lobe is involved heavily in processing sight, along with the frontal lobe, which is thought to be involved in control and attention.
The endocrine system is a slower-acting communication system that regulates the circulation of hormones, released by glands into the bloodstream. For example, cortisol and adrenaline are key hormones that facilitate the fight or flight response, a key evolutionary survival mechanism whereby the body primes itself for imminent danger (e.g. increasing heart rate, initiating sweating to cool down, dilation of pupils, sharpened sense of hearing).
Twin/family studies are useful for investigating the heritability of behaviour. For instance, research can investigate the likelihood that both of two twins develop a characteristic, known as a concordance rate. However, these studies can be time-consuming, due to long delays often required before follow-up data is collected. It is also difficult finding a large samples of participants for twin studies.
Example: Evidence has suggested that if one identical twin (monozygotic [MZ], with near-identical genetic information to the other) develops schizophrenia, there is a roughly 48% chance of the other also developing schizophrenia, whereas this is only about 17% with non-identical twins (dizygotic [DZ], who share about 50% of their genes). Such findings support that genetics play a significant part in the disorder.
Twin studies stand as a cornerstone in behavioural genetics, illuminating the intricate interplay between genetic makeup and environmental factors. They've become an invaluable tool in dissecting the nature versus nurture debate, aiding researchers in discerning the relative contributions of genes and the environment to various behavioural traits and disorders. A deeper understanding of these foundational elements can be gained by exploring the basics of genetics.
1. Genetic Control: Twins, especially MZ pairs, offer researchers an almost unparalleled control over genetic variables. This makes it easier to hone in on the effects of environmental differences.
2. Rich Data Source: Cases where twins have been separated at birth and then reared in contrasting environments are natural experiments in their own right. They offer deep insights, revealing how different upbringings can lead to variances in traits and behaviours.
1. Equal Environment Assumption: One major critique is the assumption that MZ and DZ twins experience equally similar environments. This is often not the case. MZ twins might face more identical treatments or share closer bonds, which can influence behavioural outcomes.
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