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?

Interaction between Inheritance and Environment

Genetics (inherited)

Environment (experienced)

BehaviourDiathesis-str

ess model

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.

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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

Correlation studies

No correlation Negative correlation

Positive correlation

Example: hours spent reading psychology materialsand interacting with other students and results in psychology.

Example: hours spent reading psychology materialsand interacting with other students and gender.

Example: hours spent reading psychology materialsand interacting with other students and unhappiness with the course.

Correlation studies – who do researchers study?

Twin studies

• MZ twins• DZ twins

Family studies

• (Grand)parents• Siblings

Adoption studies

• Adopted family

• Biological family

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)]

Correlation is not causation

What does this mean?

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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.

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?

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).

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Do you have questions?