1920-21.] The Annual Incidence of Intelligence. 
151 
(5) (a) Table II. gives the average mark obtained in three different 
ways of boys born in each month. 
( b ) The result marked B is the most reliable average for the usual 
reasons, the boys aged eleven being rather a clever sample. 
(c) The result of the Burt test is added for comparison. 
(6) Both diagram and table thus give clear indication that, from some 
cause, boys born in the late spring months — say March to July — are in 
danger of developing less intelligence than those born about October to 
December. But 
(a) many of the cleverest boys in the school have birthdays in the 
less intelligent period ; 
(b) some of the duller boys are brilliant enough athletically ; hence 
(c) some effect of environment may possibly be indicated ; 
(d) the experiment requires to be repeated in other localities. 
