ON THE CORRELATION BETWEEN INTELLIGENCE 

 AND THE SIZE OF THE HEAD. 



RAYMOND PEARL. 



On account of the considerable intrinsic interest of the question 

 as to whether or not there is a sensible degree of correlation 

 between intellectual capacity and the size of the brain or of the 

 head it seems desirable to have all the exact and direct evidence on 

 the matter which can be obtained. It has been alternately main- 

 tained that such a correlation does exist, and that it does not exist, 

 but until comparatively recently there have been no attempts to 

 obtain by adequate methods any definite quantitative statement 

 regarding this question. It is, I think, perfectly obvious that the 

 only way in which a definite answer may be obtained to the prob- 

 lem is to apply proper methods of reduction to a sufficiently large 

 body of homogeneous statistics which record for each individual 

 some measure of the intellectual ability on the one hand and of the 

 size of the brain or head on the other hand. It is idle to attempt 

 to reach any answer by an exammation of mdividual cases, be- 

 cause, to name one point only, our general experience teaches 

 beyond question that if such a correlation exists at all it is of a low 

 order, and in consequence even its existence, to say nothing of its 

 amount, cannot be determined from individual instances. The 

 important thing to determine first of all is whether, if we take a 

 large sample out of a homogeneous population, the individuals of 

 more than average intellectual ability possess brains or heads 

 above the average in size. It is to get evidence on this direct 

 question of fact that, so far as I understand it, the biometrical 

 work on the problem has been undertaken. 



The purpose of this paper is to present the results of the reduc- 

 tion of some new statistics which have been recently published, 

 and which show, for a reasonably homogeneous German popula- 

 tion, the relation between the horizontal circumference of the head 

 and intelligence. These admirable statistics were collected by 



