Online class - Behavioural Genetics

1. Behavioural Genetics – what does this
mean?
Humans share 93%
of their genes with
the rhesus macaque
monkey and about
99% with rats – but
what about the rest?

2. Interaction between Inheritance and
Environment
Behaviour
Environment
(experienced)
Genetics
(inherited)

3. The Challenge is to …
Discuss the extent to which genetics influence
behaviour. Try and work out how much of a certain
behaviour is inherited and how much is
environmental.
?
?

4. Correlation studies – what do
researchers measure?
What is a correlation? It is when two variables
move together, either in the same (positive
correlation) or opposite (negative correlation)
directions.
Correlation can have a value (quantitative data):
• 1 is a perfect positive correlation
• 0 is no correlation (the values don't seem linked
at all)
• -1 is a perfect negative correlation

5. Correlation studies
Positive
correlation
Example: hours spent
reading psychology materials
and interacting with other
students and results in
psychology.
No correlation
Negative
correlation
Example: hours spent
reading psychology materials
and interacting with other
students and gender.
Example: hours spent
reading psychology materials
and interacting with other
students and unhappiness
with the course.

6. Correlation studies – who do
researchers study?
Twin
studies
Family
studies
Adoption
studies
• MZ twins
• DZ twins
• (Grand)parents
• Siblings
• Adopted
family
• Biological
family

7. Correlation studies – why do
researchers study these groups?
Because they have all genes, some genes, or
no genes in common. The amount of shared
genes is the variable and the concordance
rate* for various behaviours is what is
measured.
Focus on what can be diagnosed and/or
measured: IQ, major depressive disorder,
personality, and many others.
[When comparing pairs of data, especially in twin studies, the term “concordance
rate”, expressed as a percentage, is often used as a statistical statement of the
correlation. (80% concordance rate = 0.8 correlation)]

8. Correlation is not causation
What does this mean?

9. Minnesota Twin Study
Although the original longitudinal study is now
finished, the Minnesota Center for Twin &
Family Research is still conducting studies.
See https://mctfr.psych.umn.edu/aboutus/index.html for updates.
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10. Critical Thinking about Behavioural
Genetics
• Selective placement: adoption agencies try and place children in families
that are similar to their own. Therefore the environment for a twin raised
in an adoptive family and a twin raised in the biological family may be very
similar. This is the same with adopted children, when compared with their
biological and adoptive parents – the environmental factor is difficult to
determine. (See p 28-29 of the Psychology e-text)
• Twin studies: even if raised apart, identical twins have common age,
common sex, similar appearance, similar socioeconomic and cultural
environment (usually, see above), and a common prenatal environment.
• Increasing heritability: correlations between parent and child IQs change
over time, becoming stronger as the child ages. (See Plomin and Petrill,
1997, p 56 in your Course Companion). What could this mean?
• In the Course Companion it is stated that “poverty - not genetic inferiority
– is key to understanding differences in intelligence” (p56). What could
this mean?

11. Want to test your own IQ? (And
develop your critical thinking).
Here are 3 links to online IQ tests. Try and take all 3 tests in
the same day. Ignore the results, except to compare them.
If they are different, how do you explain this? Have you
become more/less intelligent in just one day? If they are the
same, is this sufficient to say that you have this “IQ”?
http://www.free-iqtest.net/
www.learnmyself.com
http://www.iqleague.com
(Note that these are all free. The second asks for your email address,
but you can make one up).

12. Do you have questions?
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