Behavior geneticists study the genetic basis of behavior and
personality differences among people.
The more closely people are biologically related, the more genes they
Traits can be monogenic (determined by one gene) or polygenic (determined by several genes).
Researchers use heritability to determine how much of a
trait’s variation within a population is due to genes.
Types of Genetic Studies
Psychologists use family studies, twin studies,
and adoption studies to see whether, and to what extent,
characteristics are genetic.
Heredity interacts with environment to influence psychological
Evolution and Natural Selection
Evolution is the change in the frequency of genes in a
Charles Darwin proposed the theory of natural
selection, which states that inherited characteristics that give an
organism a survival or reproductive advantage are passed on more
often to future generations than other inherited characteristics.
An adaptation is an inherited characteristic that increases
in a population because it provides a survival or reproductive advantage.
Inclusive fitness is the reproductive fitness of an
individual organism plus any effect that the organism has on increasing
reproductive fitness in related organisms.
Evolution relies on mutations,or small changes
Evolutionary psychologists use evolutionary theory to explain
patterns in psychological characteristics.
Researchers study mating behavior to investigate aspects
of evolutionary psychology.
Parental investment refers to all the resources spent
to produce and raise offspring.
Sexual selection refers to the tendency of females to choose
mates based on certain characteristics, which are then passed on to their male