In the second twin study we compare the similarity once again, but this time it is with only MZs that have grown up in the same family or in different environments and see whether or not those who have grown up together are more alike than those that have grown up apart. The study came to an end resulting in that MZs that grew up together were more similar than those that grew up apart from each other. This just shows the importance of the environment in wich tey grow up in. But a real interesting fact in this study is that even separated MZs tend to be much more alike than two unrelated people that grew up in the different environment, demonstrating that once again the importance of genes. The term EXTRAVERSION refers to how impulsive and sociable the twins were, and the term NEUROTICISM refers to how anxious and moody the twins were. The table below shows the results for this study;
Looking at the table the out come that there is would be quite shocking if genes was not a factor in this equation, this is simply because the twins that were reared apart are still quite similar, but then this is assuming that personality can be well measured to a high accuracy in order to show up the differences. According to a source not all psychologists would accept such a study seriously.
Concluding that twin studies provide a powerful argument for the role of genes in affecting individual differences amongst us with respect to intelligence, personality and mental disorder. Anyhow there are problems with the studies (like most things). In the case of the separated MZs the researchers must rely on data from a small group of people who were separated a different ages and different situations. Some may even have spent considerable amount of time together before the separation or even been separated but then lived in a very similar environments. In fact because MZs look alike more than DZs, people may tend to treat them more similar manner meaning that this will become a similar environment as well as the same genes. So the meaning of all this is that when comparing the two different types of twins, MZs and DZs we can not know to what extent we are seeing the influence of genes and to what extent the effect of environment.
When looking at the plus and minus points of the study it points towards the minus, although the evidence of the importance of the role of the gene is a powerful plus. This is ruined by the not know to what extent is influenced by genes and what extent is influenced by environment, and by the study in which is shown that MZs reared together are more similar to DZs reared together, because if the MZs have a more similar environment together than the DZ, it may just as well be the identical genes lead to the greater similarity.