Questions of the Day and of the Fray number 8: Pearson, Karl, and Jaederhølm, Gustav A. 1914. Mendelism and the Problem of Mental Defect. II. On the Continuity of Mental Defect (London: Dulau and Co.). 47 pp.
Summary
Questions number 7-9 comprise a sustained critique, primarily by the Galton Laboratory, against the American Eugenics Record Office (E.R.O.) and its dogmatic application of Mendelian theory to human mental defect. See Questions number 7, Questions number 8, and Questions number 9.
This study uses psychometric methods to refute the Mendelian concept of mental defect as a “unit character” differentiated from normality.
Using modified Binet-Simon tests on 301 Stockholm “help-class” children (mentally defective) and 261 normal children, the authors demonstrated the absolute continuity of intelligence. The key findings showed that:
- Significant Overlap: Over 60% of the children classified as mentally defective possessed grades of mental defect that were found within the population of ostensibly normal children.
- Lack of Boundary: It is “perfectly idle” to speak of a sharp division; genuine mental defect could only be asserted when a child showed a mental backwardness of at least three or four years from their physical age.
- Definition of Defect: The fact that half the segregated children could not be differentiated by intelligence alone suggested that the selection criterion was likely based on factors outside of mentality, such as physical defects, poor self-control, or moral habits. They proposed the term “social inefficients” rather than “mental defectives” for this population.
Questions of the Day and of the Fray number 8
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