[stamped]University College London Penrose Papers 137/4[end stamp]
35, Lexden Road,
Colchester.
19th July 1932
Dear Lancelot,
Here are the correlations between members of families as regards mental deficiency, dullness, and normality. There were 84 families which I selected by the negative criteria that I had no idea what the deficiency was due to and so thought it might be hereditary. The correlations between parents and children are not too far out for sex-linked factors to be playing a part but the brother-sister correlations are hopelessly. The low correlations between siblings seem to be due, chiefly, to the large number of families in which only one person is affected and the rest are quite normal. On the face of it they suggest that there are non-hereditary factors involved. I will go through these families again very carefully and add some more also and try again.
[watermark]
[end]