Since 1978, researchers have studied a particular family whose members have one thing in common. they share a marked inability to control their impulses, although they all have normal iqs. for example, one brother raped his sister and later, in a mental institution, he stabbed a warden in the chest with a pitchfork. another relative tried to run his boss down with a car. two other relatives were firebugs and still another had a habit of creeping into his sisters’ bedroom and forcing them, at knifepoint, to undress. according to one of the researchers, "this is the first example showing a specific gene that changes the behavior of individuals.