Discuss the extent
to which genetics influences behavior
determine the effect of a particular gene on behavior such as psychological
traits (temperament), psychological disorders (e.g. depression or schizophrenia)
or various physiological conditions.
Study to use:
Caspi et al. (2003)
twins (MZ or identical twins) come from the same egg and share 100% of their
genes. Dizygotic twins (DZ or fraternal twins) come from two different eggs
and share around 50% of their genes. Siblings share 50% of their genes.
researchers calculate concordance rate (the likelihood or probability that
if one individual has the trait the other will also have it). The
concordance rate is assumed to establish if or to what extent a certain
trait is inherited.
studies, one twin acts as control for the other twin. The classic twin study
only studied concordance rates and did not include environmental factors. In
some cases MZ twins were raised apart and in these cases it was assumed that
differences were due to environmental factors.
research, sets of MZ are compared with sets of DZ twins for a particular
trait or disorder. High concordance rates in MZ twins and lower concordance
rates in DZ twins for the same behavior indicate that the trait or disease
is linked to genes (inherited). Differences within pairs of identical twins
are attributed to environmental factors.
Study to use:
Bouchard et al. (1990)