What are behavioral genetics? Can you give an example?

Behavioral genetics is an interdisciplinary sub-field of evolutionary biology, and it overlaps with neuroscience and psychology as well. The main theory of behavioral genetics is that behavioral and personality traits are influenced directly by biological factors and influenced both directly and indirectly by environmental elements. An example of the application of behavioral genetics is when we research the development of intelligence. Genetic abnormalities can be hereditary neuro-physiological issues, therefore influencing the development of intelligence. Behavioral genetics is in contrast, but not necessarily fully contradictory, to psychology theories that one's social environment affects the personality development of adolescents. In psychoanalysis, it is usually opined that the environment has substantial influence in the development of adolescents. For example, teaching children negative traits, such as using violence to express anger, can lead to these behaviors being displayed. In behavioral genetics, it is believed that physical abnormalities within the brain or the genetic makeup of a person are more influential in constructing personality and behavioral tendencies.
http://www.personalityresearch.org/bg.html