Pearl, Correlation in Brain-Weiglit. 475 



The weight of the brain is generally more highly correlated 

 with other characters in the female than in the male. 



6. Brain-iveight and Age and Stature. The correlation of 

 brain-weight with age is negative. This is an expression of the 

 fact that the weight of the brain diminishes with advancing 

 years. The point which I especially wished to investigate was 

 the character of the regression of brain-weight on age. If this 

 regression is linear throughout it means that the diminution in 

 brain-weight accompanying increase in age is steady and uni- 

 form throughout the adult period of life. This I found to be 

 the case within the limits of error from random sampling. 

 Beginning with about age 20 there is a steady and uniform, 

 through gradual, decline in brain-weight with advancing years, 

 up to age 80 which was the upper limit of the period investi- 

 gated. For all practical purposes the regressions may be tak- 

 en to be strictly linear. The paucity of material makes it im- 

 possible to determine with great precision the form of the re- 

 gression line, but it is quite clear that no simple curve will rep- 

 resent the regression of brain- weight on age for the series here stu- 

 died better than does a straight line. A full discussion of this 

 important matter with diagrams of the actual regression lines 

 together with the analytical data will be found in the com- 

 plete paper. The increased rate of decline of brain-weight 

 beginning at about age 50, which was expected, was not 

 found. 



The correlation between brain-weight and age is in all ser- 

 ies except the Swedish higher for the females than for the males. 

 It is suggested that in this higher correlation we may have "an 

 expression in a particular case of a greater general 'evenness' 

 of the bodily changes accompanying increasing age in the 

 female, which in turn might be due to the generally more even 

 environmental conditions to which women are subjected. It is 

 noteworthy in this connection that the correlation in respect to 

 duration of life is generally higher between pairs of female rela- 

 tives than between pairs of male relatives" (Beeton and Pear- 

 son :0i, p. 60). 



The correlation between brain-weight and stature is posi- 



