LAQ: Discuss the extent to which genetics influence behaviour.

According to the third principle of the biological level of analysis behaviour is innate, therefore, to a large extent behaviour has a genetic basis and can be explained using genetics and genetic inheritance (specific behaviours and traits may be passed by the parent to the offspring, such as temperament). Behavioural genetics investigates the effect of genetics, as well as the environment, on human behaviour. For example, certain human behaviours (such as depression) are affected by genes (a predisposition in the 5-HTT gene) However, human behaviour is very complex and it cannot be said that a single gene is responsible for a complex behaviour (such as depression), but rather, it is a combination of genetics and the environment (parenting, socioeconomic status, culture etc) that contribute to a specific behaviour, therefore, it is hard to establish a clear cause and effect relationship between a specific genetic factor (such as the 5-HTT gene) and a particular behaviour (such as depression). Finally, due to the bidirectional nature of behaviour, psychologists cannot be sure if the first variable is responsible for the second variable or vice versa (for example low levels of the neurotransmitter seratonin are related with depression but we are not able to say whether the low levels of seratonin cause depression or whether depression causes these low levels in seratonin). This essay will discuss how genetics affects the behaviours of intelligence and depression.

 Bouchard et al conducted a twin study and investigated how genetic inheritance affects the behaviour of intelligence. Participants were volunteers; some of them were twins that lived in the same environment (same house) and some paritcipants were twins that lived in different environments (adopted by different families). Bouchard measured the concordance rate for a variety of behaviours including intelligence. Participants were both monozygotic twins (identical-100% the same genes, if intelligence is believed to be innate then we would expect that the monozygotic twins would have a very high concordance rate regardless the environment they were raised up in) and dizygotic twins (twins from a different egg and sperm with 50% same genes, just like any other  siblings). Bouchard found out that the monozygotic twins that lived in different environments had a 76% concordace rate while the monozygotic twins living in the same environment had a 86% concordance rate. The dizygotic twins that lived in the same environment had a 55% concordance rate while the dizygotic twins that lived in a different enviornment had much less than that. As a control, Bouchard tested each participant twice. the results of this correlational study which was mainly surveys, questionnaires and interviews suggest that even though monozygotic twins t have 100% the same genes and you would expect them to have the same concordance rate for both environments; the environmetn is an important factor affecting intelligence since when monozygotic twins living in different environmetns had about a 10% drop in concordance rate compared to the monozygotic twins living in the same environment, it was the same for the dizygotic twins. however the results also suggest that IQ has a genetic basis since the monozygotic twins had about 30% increase in concordance rate in intelligence than the dizygotic twins suggesting that they are more similar in intelligence and therefore since they hae 100% the same genes intelligence is largely due to genetics. Bouchard concluded that environmental factors do play a role in the behaviour of intelligence since when the twins were raised in different environments they had a decrease in concordance rates than when they were raised in the same environments. An important evaluation point for the above study is that it is a correlational study meaning that the researcher is not manipulating any varibale, there is no independent variable, and he is not in control of extranous variables which may affect the results (eg. personality differences, brain damage, mood of participants etc which may affect on how the participants will do on the intellgence tests) which may affect the results therefore he is not able to establish a cause and effect relationship (problem of the third variable meaning that other extranous variables, apart from the variables being measured, may be responsible for the dependent variable). in addition, although the study provides evidence that intelligence has some genetic basis since the monozygotic twins which were 100% identical had a much higher concordance rate compared to the dizygotic twins which were only 50% identical it is hard to generalise the results to people who are not twins and from different socioeconomic and social backgrounds. The Bouchard study relates to the effect of genetics to a particular behaviour (intellligence), monozygoic twins (which are identical) had a very high concordance rate compared to dizygotic twins which suggests that intelligence is largely based on genetics; however, other factors other than genetics (the environment) also play an important role on intelligence; when twins were raised up in the same environment they had a higher concordance rate than when they were raised in different environments regardless being monozygotic/dizygotic which shows that the environment also plays a key role in the behaviour of intelligence. a

 A longitudinal study was conducted, by Caspi,  to investigate why some people  develop clinical depression after a life changing and/or stressful event while other people do not. Caspi specifically investigated the relationship between the 5-HTT gene and depression. Participants were a group with a genetic predisposition (mutation) in the 5-HTT gene (they had shorter alleles than the normal gene) and a group with the normal 5-HTT gene. Caspi found out that, following a stressful event, a large number of participants with the genetic predisposition suffered from clinical depression, while only a few participants with the norma gene suffered from clinical depression after a stressful event. It was concluded that depression is largely based on genetics, specifically in the genetic predisposition of the 5-HTT gene because a large number of participants with this predisposition developed depression; however, there were still a small number of participants with the normal gene that still developed depression which suggests that genetics is not the only factor causing depression but other factors such as the environment also play a key role. It is important to take into account that the study is correlational in nature and therefore the researcher cannot establish a clear cause and effect relationship, as there is always the problem of the third variable meaning that other factors such as the environment will affect the development of depression (therefore the researcher cannot be certain that the genetic predisposition in the 5-HTT gene causes depression). In addition, the ethical consideration of protection from harm arises in this kind of research: participants who are genetically tested and are found to have a genetic mutation in the 5-HTT gene (being aware that it is linked to depression) are likely to be very worried and stressed which may lead to psychological instability, therefore the researcher must ensure that protection from psychological (and physical) harm is minimized as much as possible. Finally, since the study is longitudinal the researcher is able to study a specific behaviour (and the evolution of the particular behaviour) over a large period of time, however, there are also large drop out rates in these kinds of studies (since participants may get tired of being part of the study) which may have an effect on the results. The Caspi study relates to the effect of genetics (the genetic predisposition in the 5-HTT gene) on behaviour (depression), since this genetic predisposition increased the chance of developing depression (participants with this predisposition were more likely to develop depression than pariticipants with the normal gene). However, other factors other than genetics, such as the environment, may affect the development of depression (since some of the pariticipants without the mutation in the gene developed depression either way)

The Wahlsten study also investigated the effect of genetics on behaviour. Wahlsten conducted a research study in France; he found that transfering an infant from a low socio economic status family to a high socioeconomic status family improved the childrens IQ by 12-16 points. Therefore, Wahlsten concluded that intelligence (even though having a genetic basis) is largely influenced by the environment; this can be shown by this very large increase in IQ points when infants moved from a low socioeconomic environment to a high socioeconomic one (this suggests that when children move from a non stimulating environment to an enriched, stimulation environment with more economic and social stability, good parenting and better eduaction their intelligence is affected which explains this rise in IQ. The study is a natural experiment and therefore the independent variable is naturally occuring and is not manipulated by the researcher, the researcher is not able to control other confounding variables which may affect the results of the study (there may be other factors, other than the change in environment which may affect this rise in IQ scores) and therefore the researcher cannot establish a clear cause and effect relationship. The ethical consideration of informed consent also arises in the study; the researcher is dealing with very young children and must have the informed consent from their legal guardians, however, since the children are changin homes, they are also changing their legal guardians so informed consent is a complicated issue (since the new guardians may disagree with the children taken part in the study. The Wahlesten study is related to the effect of genetics on  behaviour (intelligence); however, it shows that at young ages  IQ is largely affected by the environment a child is raised up in; this is shown by the large increase in IQ points when the children moved from a non-stimulating, low socioeconomic household to a high socioeconomic household suggesting that the environment plays a crucial role in the behaviour of intelligence.

In conclusion, as shown by the above studies genetics has an effect on the behaviours of depression and intelligence, but other factors, such as the environment also play a key role in these behaviours.