FIFTH LECTURE. 



INSTINCT. 



EDWARD THORNDIKE. 



I HAVE first of all a request to make of the reader. It is 

 that, in receiving and estimating what I say, he temporarily 

 discard the definitions or formulae for psychological phenomena 

 now in his mind. Many of the discussions and quarrels of 

 comparative psychology are about mere words, and are there- 

 fore fruitless. We can avoid all such if for the time being I 

 am allowed to name the phenomena, the facts about which we 

 are to think, as I please. I hope to make clear what facts I 

 am referring to in every case, and you will be at liberty to 

 rename them after your own preferences as soon as we part 

 company. 



The facts to which I refer by the words " instinctive reactions" 

 or " instinctive activities" or " instincts " are any activities which 

 do not have to be learned, which the animal is capable of without 

 experience. Let us not mind whether the act be accompanied 

 by consciousness or not, whether it represent the inheritance 

 of some ability acquired by the animal's ancestors or not, 

 whether it involve emotional feeling or not. I shall, for the 

 sake of keeping in line with customary usage, deal with such 

 instinctive activities as physiology generally leaves out, e.g., 

 instinctive fears, food preferences, motor control in running, 

 jumping, flying, etc., though breathing, defecation, sleeping, 

 etc., really deserve treatment of just the same sort as these 

 more complex activities. Under instincts, then, let us study 

 all the abilities to respond to different situations (more particu- 

 larly certain complicated external situations) which the animal 



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