The development of Penrose's ideas in genetics and psychiatry.

The article presents an analysis of Lionel Penrose's contributions to research on the role of genetics in mental deficiency. His research of the subject started with his 1931 Colchester survey where he presented a detailed clinical and genetic study of 1,2820 patients in the Royal Eastern Counties Institution. One finding of the survey indicates that there is no sharp dividing line between mental deficiency and the normal state. Moreover, both genetic and environmental aspects contribute to the occurrence of mental illness. His research developed when he became Galton professor at University College where he promoted the research on human genetics.