To what extent does genetic inheritance influence behavior? ” A debate of nature vs. nurture, as in whether it is our inherited genes or environmental factors that affect our behavior, has been going on for years. There are no true experiments on genetic inheritance influencing behavior due to ethical reasons. Only quasi-experiments and theories of pre-existing data are available that are on genetics or environmental factors affecting behavior. With the few studies existing one can still argue that genetic inheritance is a major aspect in what affects behavior but environmental factors can be more affective.
There are two main theories of human behavior. Some scientists and psychologists believe in the “nature” theory, that one behaves as they do because of their inherited genetics. Others believe in the “nurture” theory where one behaves in certain ways because they were taught to. Researches behind these theories involve studying monozygotic (MZ) twins and dizygotic twins (DZ) raised together or apart (MZA/DZA). There are only quasi-experiments and research on the differences between MZ, DZ, MZA, and DZA twins’ behavior.
Consequently there are so many other factor influences and bidirectionality that should be considered when looking at these studies. A person’s genes can affect their happiness to a certain extent. Lykken says, “It may be that trying to be happier is as futile as trying to be taller and therefore is counterproductive”. He had carried out a quasi-experiment in 1996 where he got MZ, DZ, MZA, and DZA twins to answer a questionnaire. The questionnaire was designed to measure Subjective Well-being (SWB) and the results were grouped. The correlation in the SWB scores between the MZ twins was 0. 44 and 0. 2 between MZA twins. The correlation between DZ twins was close to zero and similarly for DZA twins as well. In all, the correlation was less than 0. 05 between happiness and educational levels, income, social status, marital status, and religiosity. Therefore, according to the results, factors like education, money, or martial status have very little long-term effect on happiness. Lykken concluded that genetics have by far the strongest effect on happiness. The study had some positive qualities such as no harm involved and the large number of twins, which made the results fairly reliable.
However, there were few MZA and DZA twins and the questionnaire was not a reliable way to measure happiness. Much criticism can be made on this study because firstly it was a quasi-experiment and was carried out only on twins in Minnesota. Also, happiness cannot be measured. When answering the questions in the SWB questionnaire the twins had to compare their happiness to other people. Lykken made conclusions off of these twins’ feelings and emotions of their happiness. These were also just twins from Minnesota, in a First World country (America), and he used their results to generalize for all people.
The big question of whether intelligence is inherited or “nurtured” by one’s environment has been widely researched. The Flynn effect is a theory suggesting that IQ scores have increased over the past few generations because of environmental factors. Flynn studied differences in IQ test scores in over thirty countries and found that IQ scores on average have risen by about three points per decade. It stood out that Black Americans’ IQ scores have increase fifty percent faster than White Americans’ between WWII and now.
His explanation for the closing gap between different races’ IQ scores is that nowadays we are taught to classify our world intellectually. There is a profound change in the way we think today compared to half a century ago. We have grown to think in more abstract forms and sort our world by conceptualizing it because of the major growth in technology and science. Although, Flynn’s study is outdated and there are other factors his study does not recognize. For example, interracial mixing has increased largely as well in the past half century.
Therefore the conclusion could be bidirectional but then again the technology boom could be the cause of allowing interracial mixing. Similarly to Flynn, Turkheimer searched for data on twins in a wide range of families. He investigated the role of environment and whether heritability of intelligence is equally high in all socio-economic classes. He found that the heritability of IQ for MZ and DZ twins was very high in affluent families. Among twins who grew up in the poorest families, the MZ and DZ twins had scores that varied all the same; therefore heritability of IQ is close to zero. The effect of growing up impoverished overrules genetic nfluences on IQ but in affluent families, IQ differences can be explained by genetics. However, Turkheimer compared old data from back to the 1970s and used IQ scores of 7 year olds. Taking 7 year olds’ IQ scores and generalizing it for all ages is quite questionable. It is possible that it takes more than 7 years for environmental factors to make large impacts and that before then it is genetic inheritance impacting the most. Also, if one is born handicapped or abnormal it can impact one’s behavior the rest of their life but environmental factors could change the way the one would deal with their handicap.
In all, inherited genetics can affect one’s behavior in terms of happiness or intelligence to a certain extent and especially for people raised in affluent families. However, environmental factors can affect one’s behavior more so because there are so many impacting factors that can change how one’s genetic inheritance is used. Even though there is no clear evidence or full experiments to be certain of which affects our behaviors most, it can be speculated that genetic inheritance affects early childhood the most and then environmental factors mold how one deals with their genetic inheritance the rest of their life.