The BPS Research Digest has a concise article on a key way of determining how much genetics influences the expression of a psychological trait – the twin study.
The article is part of a new series where professional researchers are asked to write short articles on key topics.
This one is by Dr Angelica Ronald from London’s Institute of Psychiatry who researches the autism spectrum.
Twin designs address the nature-nurture question. Behaviour geneticists compare how alike one twin is with the other twin on whatever variable they are interested in; in my case this is autistic behaviours. If genes influence variation in autistic behaviours, identical twin pairs who share all their genes will be highly similar in their degree of autistic behaviours whereas fraternal twins will be much less similar. This is what we have found.
Twin studies have been essential in understanding the effects of genetics but are controversial with some researchers as there are various ways of determining the outcome which may not always be in agreement.
Link to BPSRD article ‘Why psychologists study twins’.