Turner, Homing of Ants. 413 



traces which fuse together, so that if, later, one of the processes is 

 repeated, the other will necessarily be repeated also. By asso- 

 ciative memory we mean, therefore, that mechanism by means 

 of which a stimulus produces not only the effect which corre- 

 spond to its nature and the specific structure of the stimulated 

 organ, but which produces, in addition, such effects of other 

 causes as at some former times may have attacked the organism, 

 almost or quite simultaneously with the given stimulus" (Loeb 

 '02, pp. 213 and 214). 



As to the criteria of memory, the same author writes {ihid, 

 p. 218): "It will require more observations than we have made at 

 present to give absolutely unequivocal criteria. For the present, 

 we can say that if an animal can learn, that is, if it can be trained 

 to react in a desired way upon certain stimuli (signs), it must pos- 

 sess associative memory. The only fault with this criterion is 

 that an animal may be able to remember (and to associate) and 



yet not yield to our attempts to train it The fusion or 



growing together of heterogeneous but by chance simultaneous 

 processes is a sure criterion for the existence of associative mem- 

 ory." 



If we consider the experiments herein described in the light of 

 these criteria of Loeb, we must certainly conclude that ants have 

 associative memory; for, as has been shown, ants learn by experi- 

 ence, retain what they learn in a way that can be recalled by the 

 proper stimuli, and they can be trained to do certain things. 



Some psychologists do not agree with Loeb that the mere ability 

 to learn predicates memory. There is a method of learning 

 depending on repeated blundering efforts with fortuitious suc- 

 cesses that are gradually selected which Lloyd Morgan calls the 

 method of trial and error. Such a mode of learning, some say, 

 does not indicate the existence of memory. Memory predicates 

 the existence of ideas which are associated. In learning by trial 

 and error, no association of ideas is involved; we have simply 

 assimilation of a sense impression or impressions with an impulse. 

 To use the words of Thorndike {loc.cit.,p. 71) "The ground work 

 of animal associations is not the association of ideas, but the asso- 

 ciation of idea or sense-impression with the impulse." 



HoBHOUSE ('01), who experimented on the same animals as 

 Thorndike, differs from him in his conclusions. He thinks that 

 the average laboratory psychologist has gone to extremes in his 



