2o8 The Animal Mind 



§ 60. The Psychic Aspect of Orientation to Light 



The behavior of an organism which, by the unequal 

 contraction of symmetrically placed muscles, is forced 

 around into a position directly facing or turning tail to 

 light, the light acting as a continuous stimulus and not 

 through changes in intensity, is without any parallel in 

 hxmaan experience, and hence suggests no psychic accom- 

 paniment. Yet there seems to be a considerable amount 

 of evidence that such a type of reaction does occur, given 

 the proper amount of stimulus and the proper physiological 

 condition in the animal. It is a fact of much interest, 

 however, that when we reach organisms beyond a cer- 

 tain point in the ascending scale of complexity, the tropic 

 type of response to light begins to give place to more variable 

 responses suggesting analogies with our own behavior. 

 The individual experience of an animal strongly modifies 

 its tropisms, as we shall see in a later chapter. Brundin 

 (106) says that in certain amphipod crustaceans which he 

 studied, the "mode of behavior exhibits a transition from 

 the stage at which the creature is at the mercy of its en- 

 vironment to a stage at which it is beginning to hold its 

 own against the forces which have shaped it." Quite 

 possibly, however, the ability to modify tropic response 

 by individual experience is found in all animals, and not 

 merely in those above a certain stage; it does seem to 

 be true, though, that the tropisms are more readily over- 

 thrown by other influences, the higher the animal. Thus 

 Holmes (337) says of fiddler crabs that photo tropism is 

 easily overcome by fear ; although they are strongly posi- 

 tive they will run away from a moving light. "Light," 

 he says, "is followed much as an animal pursues any other 

 object of interest " ; and Turner (728) has made similar com- 



