BEHAVIOUR GENETICS

also called pPsychogenetics the study of the influence of an organism's genetic composition on its behaviour and the interaction of heredity and environment insofar as they affect behaviour. The question of the determinants of abilities as shown through behaviour has commonly been referred to as the "nature-nurture" controversy. The relationship between behaviour and genetics, or heredity, dates to the work of the English scientist Sir Francis Galton (1822-1911). Galton studied the families of outstanding men of his day and concluded, like his cousin Charles Darwin, that mental powers run in families. Galton became the first to use twins in genetic research and pioneered many of the statistical methods of analysis that are in use today. He was the first to recognize that acquired behavioral characteristics could not be transmitted genetically. In 1918 the Scot R.A. Fisher published a paper that attempted to prove that Mendel's laws of inheritance can be generalized to show that both genes and environmental factors affect an individual's behaviour. For more than half a century scientists have been studying the relationship between IQ and genetics, and have arrived at no solid conclusions. In 1937, the U.S. psychogeneticists Horatio Newman, Frank Freeman, and Karl Holzinger studied monozygotic (MZ) or identical twins that were reared by different families to determine the effect of environment on intelligence. They found that, in general, the mental ability of identical twins was influenced far more by genetic factors than by environmental influences. In 1980 another U.S. geneticist Robert Plomin concluded, on the other hand, that genetic differences account for about half of IQ variance.