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Behavioural genetics, also commonly referred to as behaviour genetics, is the field of study that examines the role of genetics in animal (including human) behaviour. Often associated with the "nature versus nurture" debate, behavioural genetics is highly interdisciplinary, involving contributions from biology, genetics, epigenetics, ethology, psychology, and statistics. Behavioural geneticists study the inheritance of behavioural traits. In humans, this information is often gathered through the use of the twin study or adoption study. In animal studies, breeding, transgenesis, and gene knockout techniques are common. Psychiatric genetics is a closely related field.

History
Sir Francis Galton, a nineteenth-century intellectual, is recognized as one of the first behavioural geneticists. Galton, a cousin of Charles Darwin, studied the heritability of human ability, focusing on mental characteristics as well as eminence among close relatives in the English upper-class. In 1869, Galton published his results in Hereditary Genius. In his work, Galton "introduced multivariate analysis and paved the way towards modern Bayesian statistics" that are used throughout the sciences—launching what has been dubbed the "Statistical Enlightenment". Galton is often credited as the pioneer of eugenics. Subsequently, Adolf Hitler is believed to have been motivated by Galton's work in enacting the Final Solution during World War II.

In 1951, Calvin S. Hall in his seminal book chapter on behavioural genetics introduced the term "psychogenetics", which enjoyed some limited popularity in the 1960s and 1970s. However, it eventually disappeared from usage in favour of "behaviour genetics".

Behaviour genetics, per se, gained recognition as a research discipline with the publication in 1960 of the textbook Behavior Genetics by J.L. Fuller and W.R. Thompson. Nowadays, it is widely accepted that most behaviours in animals and humans are under some degree of genetic influence.

Underscoring the role of evolution in behavioural genetics, Theodosius Dobzhansky was elected the first president of the Behavior Genetics Association in 1972; the BGA bestows the Dobzhansky Award on researchers for their outstanding contributions to the field. In the early 1970s, Lee Ehrman, a doctoral student of Dobzhansky, wrote seminal papers describing the relationship between genotype frequency and mating success in Drosophila,  lending impetus to the pursuit of genetic studies of behaviour in other animals. Studies on hygienic behavior in honey bees were also carried out early in the history of the field. The social behaviour of honey bees has also been studied and recent work has focussed on the gene involved in the foraging behaviour of Drosophila; this essentially allowed for deriving a relationship between gene expression and behaviour, where the gene regulating foraging behaviour in Drosophila also regulated social behaviour in bees.

Methods
The primary goal of behavioural genetics is to establish causal relationships between genes and behaviour. One common approach is the reductionist approach. Under this approach, scientists first observe a psychological or behavioural function (e.g., schizophrenia). Next, using known functions of brain systems and neurotransmitter systems, scientists correlate behaviour to these brain areas (e.g., excess glutamate release may stimulate excess dopamine in the limbic system leading to schizophrenic symptoms). Once scientists are able to map behaviour to biological systems, they can then turn to genetics to understand the development of these biological systems (e.g., an abnormal glutamate gene could be a candidate gene for schizophrenia). Initial attempts to associate particular genes (or at least chromosomal positions) to behaviour often involve a search for Quantitative trait loci (QTL). Other methods used with human populations involve twin studies and adoption studies. These two methods attempt to separate environmental contributions to behaviour from genetic contributions.

The Human Genome Project has allowed scientists to understand the coding sequence of human DNA nucleotides. Once candidate genes for behaviours are discovered, scientists may be able to genetically screen individuals to determine their likelihood of developing certain pathologies.

With non-human animals, selection experiments have often been employed. For example, laboratory house mice have been bred for open-field behaviour, thermoregulatory nesting, and voluntary wheel-running behaviour.

Notable behavioural geneticists
Notable behavioural geneticists include Dorret Boomsma, Wim Crusio (the founding editor of the journal Genes, Brain and Behavior), John DeFries, Lindon Eaves, David Fulker, Irving Gottesman, John K. Hewitt, Kenneth Kendler, John C. Loehlin, Nick Martin, Gerald McClearn, Robert Plomin, Theodore Reich (a pioneer in psychiatric genetics), Hans van Abeelen, and Steven G. Vandenberg (the founding editor of the journal Behavior Genetics).

Journals
Behavioural geneticists are active in a variety of scientific disciplines including biology, medicine, pharmacology, psychiatry, and psychology; thus, behavioural-genetic research is published in a variety of scientific journals, including Nature and Science. Journals that specifically publish research in behavioural genetics include Behavior Genetics, Molecular Psychiatry, Psychiatric Genetics, Twin Research and Human Genetics, Genes, Brain and Behavior, and the Journal of Neurogenetics.