A condition in which a male is born with two X chromosomes, as well as the Y chromosome. Individuals tend to be unusually aggressive. (Tanenbaum, Joe. Male & Female Realities. p 134. NV: Robert Erdmann Publishing, 1990.)

A condition that results from an imbalance in hormonal secretions that causes a delay in physical maturation. Occurs in males only. They tend to be tall, lean, with breast enlargement, small or undeveloped testes, and limited sex drive (about 25% of have some mental defect). (Stump, Jane Barr, PhD. What’s the Difference? p 112. NY: William Morrow and Company, Inc., 1985.)

Perhaps nearly half a million males in the United States have Klinefelter’s syndrome: a XXY chromosomal pattern, characterized by small testicles and lowered sexual drive, but normal male visual-spatial skills. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 70-80. NY: Arbor House Publishing, 1983.)