"XYY" Chromosome disorder was first discovered in 1961 by geneticist, Avery Sandberg. After the discovery of XYY chromosome disorder many researchers started to look into it seriously. One geneticist, Patricia Jacobs, conducted a study at a maximum security hospital in Scotland. She found that 1 out of 28 patients within the hospital was of the XYY karyotype. After this it was a common belief that males with the XYY karyotype were more aggressive than average males, but it was soon discovered that many early studies of Jacob's Syndrome were flawed as the groups being tested were selected and not randomized. They were testing only men who were of above average height which is a common characteristic of Jacob's Syndrome. Today we have a far better understanding of the disease. Most XYY males have similar IQ levels as non XYY males and only show two key physical differences, one being height, the other aggressive acne during adolescence.