ON THE RELATIONSHIP OF INTELLIGENCE TO SIZE 
AND SHAPE OF HEAD, AND TO OTHER PHYSICAL 
AND MENTAL CHARACTERS. 
By KARL PEARSON, F.R.S. 
(1) Introductory. In two earlier memoirs* my co-workers and I have dealt 
with certain of the present problems. The methods then used by us were such as 
are suitable for dealing fairly rapidly with large masses of material, and by those 
methods the conclusions drawn were : 
(a) that there is a slight correlation between size of head and general 
intelligence f, 
(b) that this correlation is not sensibly increased by allowing for the size 
of the body relative to the size of the headj, 
(c) that the correlation is so small that it would be absolutely idle to 
endeavour to predict the intellectual ability of an individual from his or her 
head measurements^. On the other hand, if a population were divided into those 
with large and those with small heads, we should expect to find a very slight 
balance of average intelligence in the former group. 
The present more precise and extended investigation is based upon the more 
elaborate statistical reductions carried out during the last few years in my Bio- 
metric Laboratory. 
The material dealt with is the same, namely : 
(i) The head measurements of upwards of 1000 Cambridge graduates. I have 
already expressed my thanks to the Cambridge Anthropometrical Committee for 
this material, and to Mr W. H. Macaulay of King's College, and the University 
Registrary for supplementing the measurements with ample particulars of the 
examinational standing of each graduate. 
* R. S. Proc. Vol. G9, pp. 333—342, 1902 ; R. S. Proc. Vol. 71, pp. 106—114, 1902. 
t R. S. Proc. Vol. 69, p. 339. 
t R. S. Proc. Vol. 71, p. 112. 
§ R. S. Proc. Vol. 69, p. 340. See also a series of letters to the British Medical Journal, Jan. 27 — 
March 17, 1906, and Biomctrika, Vol. ni. p. 391 et seq. 
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