Genetic basis of behaviour examines the interaction between genes and environment in shaping behaviour. According to the interactive theory of development, genes and environment work together to influence behavioural phenotypes. Behavioural development requires both genetic and environmental factors, as seen in honey bee foraging behaviour which progresses through different stages based on age and hormone concentration. A single gene difference can lead to large behavioural differences, as shown in knockout experiments where mice lacking the fosB gene show no parental care behaviours. Both nature and nurture interact to produce behaviour.