EVOLUTION OF INTELLIGENT BEHAVIOUR 163 
intentional condensation and concentration of knowledge at a 
higher stage of mental development. 
The omission of detail and the survival of the salient 
features is well known to us in the familiar facts of memory. 
We have seen thousands of sheep and oxen, no two of which 
are probably alike in all their external details as presented to 
vision. But we remember what a sheep or an ox looks like, 
and many of us can form a visualized image of either of these 
animals. This, however, is not the re-presentative image of any 
particular sheep or ox. It is what psychologists term a generic 
image. It is like a composite photograph made by superimpos- 
ing on the same plate a number of individual images so that the 
salient features which all possess in common stand out clearly 
by their coincidence on the plate, while the distinctive details 
are but dimly presented. Thus does memory preserve the 
essentials common to many impressions while the distinguishing 
details are lost and fade, eliminated by forgetfulness. And 
thus in the experience which intelligence practically utilizes 
are the net results of a thousand particular impressions con- 
densed in one effective image. 
Condensation of experience is also effected by the elimina- 
tion, under the guidance of consciousness, of those modes of 
behaviour which are not efficacious—a process to which Pro- 
fessor Mark Baldwin applies the phrase Functional Selection. 
There is a tendency at first to the overproduction of relatively 
useless actions. The multifarious random movements of the 
human infant, though their inexactness renders the child 
terribly helpless, afford a wide store of plastic material which 
intelligence can guide to its appropriate use. And the pro- 
longed period of pupilage in the child is correlated with an 
unsurpassed range of combination and recombination of the 
abundant plastic material. The hereditary legacy, though it 
contains fewer drafts for definite and specific purposes than are 
placed to the credit of an animal rich in instinctive endowment, 
affords a far larger general fund on which intelligence may 
draw for the varied purposes of the freer financial existence 
of a rational being. 
