TRIAL AND ERROR REACTIONS IN MAMMALS 57 



ence. We must have knowledge, therefore, of the genetic rela- 

 tionships, not only of the adequately adaptive end-products in 

 behavior, but of the reactive tendencies that lead to these end- 

 products. 



The present investigation becomes intelligible only when 

 account is taken of the fact that it seeks to deal with the funda- 

 mental factors on which adaptation depends, rather than with 

 the ultimate effects of experience on behavior. Figure III 

 depicts, therefore, roughly determined curves of reactive ten- 

 dency, and not curves of learning. Since their value as curves 

 of reactive tendency will depend on the accuracy with which 

 the objective facts are translated into terms of psychic entities, 

 we are confronted by the difficult task of establishing an objec- 

 tive criterion of the subjective. How may we recognize a reactive 

 tendency in the behavior of our subjects? During the interpre- 

 tations that follow, a tentatively constructed criterion will be 

 adhered to: A mode of adjustment which appears, disappears 

 and reappears consistently with ascent or descent of the age and 

 phyletic scales may be looked upon as an expression of a definite 

 reactive tendency. 



If this criterion be accepted, a tremendous amount of detailed 

 investigation will be required to establish conclusively the ex- 

 istence of even a few reactive tendencies as biological entities. 



With the above in mind as a qualification of what follows, we 

 may proceed to an interpretation of results by first presenting a 

 summary of the, values for reaction contained in the experiment : 



(i) All of the subjects brought to the formal experiment a 

 more or less definite awareness of the four exit doors as possible 

 means of escape from the apparatus, hence the demand for 

 adjustment was essentially contained in the mere necessity of 

 clawing, scratching or pushing at one or more previously mobile 

 objects (all of the exit doors were left unlocked during the pre- 

 liminary training) until activity proved successful. 



(2) Without exception, all of the subjects gave definite evi- 

 dence of trying for success (escape from the apparatus) until 

 success was attained. 



(3) For every subject a considerable percentage of trials led 

 to more or less unsuccessful activity (trying locked doors). 



(4) In every case the individual trial was terminated by a 

 definitely directed activity (trying the unlocked door). 



