One indication that behavior has a genetic basis is that behavior is often species specific. Examples include the warning behavior of prairie dogs or the mouth to mouth sharing of blood amongst vampire bats. The closer our genetic resemblance is to a certain species, the more behaviors we have in common. Since long it has also been known that behavior can be bred true, which is the reason why some breeds display specific behaviors.
Behavior is also known to change in response to changes in biological structures or processes. Examples include the use of the SSRI drug which alters the reuptake of serotonin in the synapses and consequently our mood, or the loss of important cognitive functions due to brain damage. As the anatomical structure and the physiological processes depend on our DNA we can infer that genes indirectly influence our behavior. It is important to bear in mind that the brain can alter its structure from experience, but this capacity must clearly be genetically determined.
Most researchers agree that all behaviors are more or less indirectly influenced by genes. Where they disagree is the extent to which genes influence behavior. Some behavior also seems to be more influenced by genes than others. The influence of cognitive, social and cultural factors on behavior cannot be denied, and even though there may be a genetic predisposition for many disorders, the extent to which the genotype is expressed in its phenotype will depend on environmental influences. The stress-vulnerability model, for instance, assumes that the onset and symptoms of mental disorders are influenced by three interacting factors; biological, environmental and protecting factors that may protect the individual against development of a disorder.
A study that illustrates the...