# Mental defectives, part ii

I did on a previous occasion write about the seemingly powerful relationship between the number of radios in the U.K, and the number of registered mental defectives in that country. In Google books, I recently found a 1958 book titled Principles of Statistical Techniques, which contains examples based on that remarkable dataset, the number of mental defectives in England and Wales.

The passage in question uses the “mental defectives” data from 1935 through 1946 to illustrate the ability to mislead through the use of graphs and charts. The graphs below are courtesy of Mathematica but closely replicate those in the original text.

```In[]:= mentalDefectives = {{1935, 86086}, {1936, 88060}, {1938, 92299}, {1939, 99144}, {1940, 101364}, {1941, 100876}, {1942, 98125}, {1943, 98434}, {1944, 99608}, {1945, 102225}, {1946, 102390}};```

``` In[]:= ListPlot[mentalDefectives, PlotRange -> {86000, 102500}, AxesOrigin -> {1934, 86000}, AxesLabel -> {"Year", "Number of\nmental defectives"}, AspectRatio -> 2, PlotMarkers -> {Automatic, Small}] In[]:= ListPlot[mentalDefectives, PlotRange -> {0, 120000}, AxesOrigin -> {1935, 0}, AxesLabel -> {"Year", "Number of\nmental defectives"}, PlotMarkers -> {Automatic, Small}] ```

As explained in the original text, “The impression obtained from the first graph is that there was a staggering rise in the number of mental defectives in little more than a decade, whereas the second graph gives the impression of a much slower and more gradual increase. These rather different impressions are obtained, of course, by tampering with the horizontal and vertical scales used. . . . it is essential to recognize the importance of supplying graphs, as well as tables, with full and clear labelling and if possible, the source of the information.”

Frankly, their efforts seem pretty basic. We could further steepen the first graph through population adjustment, adjustment for number of doctors, and other techniques.

In googling for more on this remarkable dataset, I found letters to the editor of The British Medical Journal in which one R.A. Gibbons of London, S.W., argues that forced sterilization of mental defectives is not sufficient to protect “the race,” and that it is necessary to sterilize also those people who “from pronounced family history” are certain to “produce idiots.” Dr. Gibbons apparent delivered a paper on this topic to the Obstetrical Section of the Royal Society of Medicine and had in published in the Journal on March 18, 1922. In this letter, he refers to “over 12,000 registered mental defectives for whom [British citizens] are taxed.”

The reference to taxation feels terribly modern (“certainly their plight tugs at the heartstrings, but you just can’t care for everybody and it wouldn’t be fiscally prudent to allow them to run amok.”)

Germany is most famous for eugenics programs, but similar sterilizations of mental defectives were taking place in the United States in the early and mid 20th century. I’ll leave that for another post.