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Tasmania - Legislation

Mental Deficiency Act (1920 - 1963)

Principal Act

The Mental Deficiency Act 1920 established the State Psychological Clinic which diagnosed mental deficiency, now known as intellectual disability. The Act also established the Mental Deficiency Board which oversaw the management of children and adults classified as mentally deficient by the Clinic. The Act was influenced by the eugenics movement and based on similar legislation passed in the United Kingdom in 1913.


Edmund Morris Miller, the Professor of Philosophy and Psychology at the University of Tasmania, and an adherent of eugenics, was the main driving force behind the Act.

The Act specified four categories of mental deficiency. They were:

  • 'Idiots' who were considered to be 'so deeply defective in mind' that they could not protect themselves from the ordinary dangers of life.
  • 'Imbeciles' who had some capacity to care for themselves but as adults would not be able to look after their affairs and as children could not be taught to do so.
  • 'Feeble-minded' who required 'care, supervision, and control for their own protection or the protection of others'. Such children could not benefit from school.
  • 'Moral imbeciles' who showed 'some permanent mental defect coupled with strong vicious or criminal propensities on which punishment has little or no deterrent effect'.

Adults or children classified under the Act could be sent to an institution or placed in the care of a guardian.

Adults might include a single woman giving birth to a child while receiving an income from the state.

The Director of Education was obliged to notify the Chairman of the Mental Deficiency Board of any children suspected of having a 'mental deficiency'.

The Act made provision for special Homes to be established where children with a diagnosis of mental deficiency could be trained to lead useful and happy lives.


 1920 - 1963 Mental Deficiency Act
       1963 - 1999 Mental Health Act 1963
             1996 - 2014 Mental Health Act 1996
                   2014 - Mental Health Act 2013

Related Glossary Terms

Related Organisations


Journal Articles

  • Evans, Caroline and Parry, Naomi, 'Vessels of Progressivism? Tasmanian State Girls and Eugenics, 1900-1940', Australian Historical Studies, vol. 32, no. 117, University of Melbourne, Melbourne, 2001, pp. 322-333. Details
  • Rodwell, Grant, ''If the feeble-minded are to be preserved': special education and eugenics in Tasmania, 1900-1930', Issues in educational research, vol. 8, no. 2, 1998, pp. 131-156. Also available at Details


  • 'The mental deficiency bill, 1920:' report of Select Committee with minutes of proceedings and evidence, House of Assembly, 1920. Details

Online Resources

Sources used to compile this entry: 'Care of mental deficients: the bill before parliament: scientific treatment and supervision', The Mercury (Hobart), 23 September 1920, p. 3,

Prepared by: Caroline Evans