2.2 Genetics and behaviour
Discuss the extent to which genetics
influence behaviour
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What is intelligence quotient (IQ)?
Should indicate one’s genetically endowed
intellectual potential
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The abbreviation "IQ" comes from the German
term Intelligenz-Quotient, originally coined by
psychologist William Stern.
When modern IQ tests are devised, the mean
(average) score within an age group is set to
100 and the standard deviation (SD) almost
always to 15.
Thus, the intention is that approximately 95%
of the population scores within two SDs of the
mean, i.e. has an IQ between 70 and 130.
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IQ scores are used as predictors of educational
achievement, special needs, job performance
and income.
What about crime? Read p. 61-63 if you want to
find out and there is an article online Seeking
the criminal element
Answer questions in groups after you have tested
an IQ test:
1.
Do you think that these tests appropriately
evaluate your intelligence?
2.
Do you feel that the tests were adequate? Why or
why not?
3.
How would you change the tests to make them
reflect more accurately what you consider to be
your “intelligence”?
http://www.mensa.se/provtest
http://www.mensa.org/
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Alfred Binet a pioneer in intelligence research,
beginning of the 20th century
 Pr. Richard J. Herrnstein
& Charles Murray 1994,
Harvard: The Bell Curve
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- The Bell Curve is a best-selling but
controversial 1994 book. Its central argument is
that intelligence is a better predictor of many
personal dynamics, including financial
income, job performance, chance of unwanted
pregnancy, and involvement in crime than are
an individual's parental socioeconomic status,
or education level. The book also argues that
those with high intelligence, the "cognitive
elite", are becoming separated from those of
average and below-average intelligence, and
that this is a dangerous social trend.
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What is it?
How can it be measured?
Charles Spearman – theorized that there is a
general intelligence factor, which he called the “g”
factor.
Modern intelligence testing attempts to assess this
“g”
But the question is: where does “g” come from?
Is there any difference between men and women?
Bouchard and McGue (1981) reviewed 111
studies from around the world of IQ
correlations between siblings
A meta-analysis
Results: the closer the kinship, the higher the
correlation for IQ
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This supports the idea that IQ mostly derives
from our genes.
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The Minnesota Twin Study by Bouchard et al
1990
Longitudinal study since 1979 & cross-cultural
study. Use media to recruit participants.
MZA (identical twins raised apart) compared
to MZT (identical twins raised together)
The mean age was 41 years (start of the study),
differ from most other research which is
carried out on adolescents
Each twin completed 50 hours of testing and
interviews
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The concordance rates of intelligence can be
found in a table on p. 55
The study concluded that 70% of intelligence
can be attributed to genetic inheritance –
leaves 30% to other factors
Evaluation?
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Media coverage to recruit participants (selfselected sample)
Ethical concerns – reunited the twins
No adequate control to establish the frequency
of contacts between the twins prior to the study
“equal environment assumption” – are all
twins treated the same way (even MZ twins?)
No cause and effect
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Scarr and Weinberg (1977) and Horn et al
(1979) studied parents who raised both
adopted and natural children
So same environment – any differences should
be due to… what?
Found no significant difference in IQ correlations!
Very interesting findings
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Another study by Wahlstein (1997) in France
found that transferring children from low socioeconomic status family to one where they are high
socio-economic status improved childhood IQ
scored by 12-16 points (about one SD)
Shows that an enriched environment may raise IQ
in children.
Does this resemble to something else we have studied?
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1.
2.
3.
4.
Think critacally – using the
following:
Method?
Ethics?
Gender?
Culture?
Found out (p.56) and answer in writing:
1. What is eugenics?
2. What is the Less effort hypothesis?
3. Does IQ change over time?
4. Which factor is the most important
environmental factor in development of IQ?
5. Why has the average mean on IQ tests been
going up over the years?
6. Read the handout “the development of IQ test
performance” and summarize the “two sides”
with 2-3 arguments on each side – to be handed in
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Read the article: Eugenics Revisited and note
down a couple of questions that you can
discuss in groups
We will discuss the article using “save the last
word for me”