Lionel Penrose

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Lionel Penrose
Born Lionel Sharples Penrose
(1898-06-11)11 June 1898[1]
Died 12 May 1972(1972-05-12) (aged 73)
Alma mater St. John's College, Cambridge
Known for Penrose triangle
Penrose method
Penrose stairs[2]
Penrose's Law[3][4]
Penrose square root law
Penrose–Banzhaf index
Awards Fellow of the Royal Society[1]
Lasker Award[5]
Scientific career
Institutions University of Cambridge
University College London

Lionel Sharples Penrose, FRS (11 June 1898 – 12 May 1972) was a British psychiatrist, medical geneticist, mathematician and chess theorist, who carried out pioneering work on the genetics of mental retardation.[4][6]


Penrose was educated at the Downs School, Colwall and the Quaker Leighton Park School, Reading. On leaving school in 1916, he served, as a conscientious objector, with the Friends' Ambulance Unit/British Red Cross in France until the end of the First World War. He went on to study at St. John's College, Cambridge; he was a Cambridge Apostle.


Penrose's "Colchester Survey" of 1938 was the earliest serious attempt to study the genetics of mental retardation. He found that the relatives of patients with severe mental retardation were usually unaffected but some of them were affected with similar severity to the original patient, whereas the relatives of patients with mild mental retardation tended mostly to have mild or borderline disability. Penrose went on to identify and study many of the genetic and chromosomal causes of mental retardation (then called mental deficiency). This body of work culminated in the book, The Biology of Mental Defect (Sidgwick and Jackson, Ltd., London, UK, 1949).

Penrose was a central figure in British medical genetics following World War II. From 1945 to 1965 he occupied the Galton Chair at the Galton Laboratory at University College London. He received a number of awards and honours including the 1960 Albert Lasker Award for Basic Medical Research.[5] The Lasker citation read:

"Professor Penrose and his associates have been responsible over the years for studies which touch all aspects of human genetics, include genetic analyses of most of the known hereditary diseases, contributions to mathematical genetics, biochemical genetics, the study of gene linkage in man, and theoretical work on the mutagenic effect of ionizing radiations. Most recently their attention has been turned to abnormalities of human chromosomes associated with congenital defects, particularly mongolism (Down syndrome)."[5]

Penrose's Law[3][4] states that the population size of prisons and psychiatric hospitals are inversely related, although this is generally viewed as something of an oversimplification.[7]

Penrose, a member of the Society of Friends (Quakers), was a lead figure in the Medical Association for the Prevention of War in the 1950s.

Penrose developed the Penrose method, a method for apportioning seats in a global assembly based on the square root of each nation's population. Such a voting system is based on the voting power of any voter (measured by the Penrose–Banzhaf index) decreasing with the size of the voting body as one over its square root. See also Penrose square root law.


Penrose married Margaret Leathes in 1928 and they had four children:

After Penrose's death, Margaret married the mathematician Max Newman (1897–1984). She died in 1989.

Penrose' father was James Doyle Penrose. His mother was Elisabeth Josephine Penrose (nee Peckover) and his brother was Sir Roland Penrose, both British artists.[8][9]


  1. ^ a b Harris, H. (1973). "Lionel Sharples Penrose 1898-1972". Biographical Memoirs of Fellows of the Royal Society. 19: 521–561. doi:10.1098/rsbm.1973.0019. JSTOR 769572. PMID 11615728. 
  2. ^ Penrose, L. S.; Penrose, R. (1958). "Impossible Objects: A Special Type of Visual Illusion". British Journal of Psychology. 49 (1): 31–33. doi:10.1111/j.2044-8295.1958.tb00634.x. PMID 13536303. 
  3. ^ a b Hartvig, P. L.; Kjelsberg, E. (2009). "Penrose's Law revisited: The relationship between mental institution beds, prison population and crime rate". Nordic Journal of Psychiatry. 63 (1): 51–56. doi:10.1080/08039480802298697. PMID 18985517. 
  4. ^ a b c Penrose, L. S. (1939). "Mental Disease and Crime: Outline of a Comparative Study of European Statistics". British Journal of Medical Psychology. 18: 1–15. doi:10.1111/j.2044-8341.1939.tb00704.x. 
  5. ^ a b c Lasker Award to LS Penrose
  6. ^ Bewley, T. (2000). "Lionel Penrose, Fellow of the Royal Society". Psychiatric Bulletin. 24 (12): 469. doi:10.1192/pb.24.12.469. 
  7. ^ Prins, Herschel (2012), Offenders, Deviants or Patients? (3rd ed.), Routledge, p. 50, ISBN 9781135447311, Careful examination ... reveals that such a state of affairs is not as clear cut as Penrose and other later writers have suggested. 
  8. ^ A. M. Cooke (2004). "Penrose, Lionel Sharples". The Oxford Dictionary of National Biography. doi:10.1093/ref:odnb/31537. 
  9. ^ Laxova, R. (1998). "Lionel Sharples Penrose, 1898-1972: A personal memoir in celebration of the centenary of his birth". Genetics. 150 (4): 1333–1340. PMC 1460427Freely accessible. PMID 9832513.