THE ASSOCIATIVE PROCESSES IN ANIMALS. 91 



which they have not encountered for a long while. Dogs, cats, 

 chicks, and fishes tested after an interval of from six to eighty 

 days, either manifested as perfect associations as ever, or formed 

 such after far fewer experiences than were needed originally. 1 

 For instance, the cat that had learned to discriminate between 

 " I must feed those cats " and " I will not feed them " was, after 

 eighty days, given twenty-five trials with the first signal and 

 fifty with the other (all being mingled together indiscrimi- 

 nately). She reacted correctly to every one of the twenty-five 

 signals and by the end of the fifty reacted to that signal as well 

 as she did after 350 trials originally. 



The degree of permanence of these associations, once they 

 are formed, vastly increases their utility. It allows experiences 

 rarely met with to still, little by little, build up habits. It allows 

 the experience of certain localities, for instance, to be useful 

 again, even if the locality is not revisited for a considerable 

 time. It lets the animal's past influence its present conduct 

 in all sorts of ways. 



It seems hardly necessary to make any statement about the 

 general usefulness of the power of association in securing sur- 

 vival. If our view of the process is correct, it is a process of 

 selection among reactions, not by eliminating the animal that 

 does not react suitably and so developing a stock with certain 

 instincts, but by eliminating the unsuitable reaction directly by 

 discomfort, and also by positively selecting the suitable one by 

 pleasure, and so developing certain associations in the individ- 

 ual. It is, then, selection within the individual that is the great 

 case of plasticity, and is of tremendous usefulness, in that it 

 definitely enables the animal to modify his acts and so meet 

 varieties and modifications of environment. New feeding 

 grounds, new foods, new friends, new enemies are dealt with { 



by virtue of it. " He who learns and runs away, will live to 

 learn another day." 



TEACHERS' COLLEGE, COLUMBIA UNIVERSITY. 



1 Only one case out of over forty was an exception to this rule. 



