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1st Year Psychology Essays
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covering IQ and hereditary, depression and self-harm and Schizophrenia and the effectiveness of antipsychotics
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Student id: 5607088 Word Count: 987IQ, hereditary or environmental?
IQ is short for intelligence quotient, it is a number which represents an individual’s
reasoning ability, which is tested via various problem solving tests. The result is compared to
the norm for a person of their age. A genetic influence is apparent towards intellectual
ability (Bouchard and McGue, 1981), however it can be argued that there is an
environmental influence as well, as Rowe, Jacobson and Van den Oord (1999) have
explained. Many studies in this field have been twin studies which enable researchers to
clearly observe the different effects between genes and the environment.
As I mentioned above Bouchard and McGue summarised the results of 111 studies, and it
indicated that there is a hereditary similarity in measured intelligence (IQ). This was shown
by a consistent average correlation with polygenic mode of inheritance. This meta-analysis
shows that there is an association between the variables, therefore genes do contribute to
our IQ. Another study that shows an association is a twin study by Lynn and Hattori (1999).
They looked at 543 monozygotic twins and 134 dizygotic twins. They found that
monozygotic twins had a higher correlation than the dizygotic twins, this shows, as
monozygotic twins share the exact same genes, that genetics do play a big part and also
suggesting, as dizygotic has a lower correlation, that environment doesn’t play as big a part
as genetics when it comes to intelligence. A family design with twins, their siblings and their
parents (Leeuwen, Van den Berg and Boomsma, 2007) is an enhanced way at looking deep
into the hereditary roots. They used a Raven Progressive Matrices test to measure IQ. They
found that parents IQ were similar to one another and with monozygotic twins, correlations
between genes and IQ were higher than first degree relatives. They suggested that a model
proving that this was due to phenotypes was more superior to a model which suggested this
was due to environmental factors. Therefore again showing that genes play a bigger role
than the environment. All this research indicates that genes play a big role to our
intelligence, it is reliable and consistent with regular occurring patterns.
On the other hand Dickens and Flynn (2001) suggest that there is actually a powerful role
for the environment on IQ, environmental effects are short lived in children as they decay
quickly, therefore genes play a role in a child’s IQ. However with adults, IQ is influenced by
the environment in which surrounds them. They showed that enrichment programmes can
boost IQ and this is an environmental effect, such things can develop phenotypic traits. This
therefore suggest that even though there is a genetic link with IQ, it is only prominent in
children and in adults it is the environment that shapes their intelligence. Rowe, Jacobson
and Van den Oord (1999) have similar results. They found that if the parents had more than
a high school diploma, it was more likely the child to have a higher IQ, suggesting it’s
heritable, however in modern society we have institutions that are intellectually stimulating,
such as schools and tutors, which could help increase IQ. However that is not the case with
the working class who may also be well educated, as they live in a different environment to
someone of middle class. They state that children, even with parents with a higher IQ, may
not themselves develop the phenotype if they live in a poor area which lacks intellectually
stimulating institutions. This is a big environmental influence which can override the
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