Sometimes referred to as supermales, individuals with a double dose of Y chromosome (XYY) are often very tall and masculine looking, and are over-represented among prisoners who have committed violent and sexual crimes. (Wilson, Glenn. The Great Sex Divide. p 75-76. England:Peter Owen Publishers, 1989.)

Males with a XYY chromosome pattern tend to be more impulsive, aggressive, and antisocial than other males. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 80-90. NY:Arbor House Publishing, 1983.)