Sage-Tips

Do twin studies have overestimated heritability?

Whether twin studies have overestimated heritability for human traits, especially social and behavioural traits, remains controversial [4]. For height, by 2010 around 40 variants had been identified that collectively explained around 5\% of the variation in height, compared to a twin heritability of around 80\% [5].

What is the problem with twin studies?

Put another way, twin studies fail to separate the effects of genes and the prenatal environment. This failure casts doubt on claims of the relative effects of genes and environment on intelligence, psychiatric disorders, personality and other psychological variables, and other conditions.

What accounts for missing heritability?

The “missing heritability” problem is the fact that single genetic variations cannot account for much of the heritability of diseases, behaviors, and other phenotypes.

Why are adoption studies better than twin studies?

Twin studies are much better at studying the effects of nature (genes). High concordance between MZ twins tells us more about genetic influences than high concordance between children and their biological parents. On the other hand, adoption studies are much better at studying the effects of nurture (upbringing).

What role do twin studies play in regards to determining intelligence?

Family studies show that intelligence tends to run in families. Twin studies show a higher correlation between identical twins in IQ than between fraternal twins. This holds true even when identical twins reared apart are compared to fraternal twins reared together.

Is it possible for a character to vary in a population and have a heritability of 0?

A heritability close to zero indicates that almost all of the variability in a trait among people is due to environmental factors, with very little influence from genetic differences.

What is the future of twin studies in genetics?

Twin studies estimate the heritability of a trait, but molecular genetics attempts to pinpoint the effects of a particular gene. The future of twin research will involve combining traditional twin studies with molecular genetics research, according to Hewitt, who believes that day is already here.

What can twin studies tell us about traits?

Researchers have used twin studies to try to disentangle the environmental and genetic backgrounds of a cornucopia of traits, from aggression to intelligence to schizophrenia to alcohol dependence.

What are the different types of twin study design?

The original twin study design has expanded to include studies of twins’ extended families, longitudinal studies and other variations. Some of these variations allow researchers to address previous limitations–they can investigate the effects of nonrandom mating, for example, by including the spouses of twins in studies.

Do identical twins share the same environment?

But despite the popularity of twin studies, some psychologists have long questioned assumptions that underlie them–like the supposition that fraternal and identical twins share equal environments or that people choose mates with traits unlike their own. The equal environments assumption, for example, has been debated for at least 40 years.