122 MIND IN EVOLUTION CHAP. 



There is a further point. In the instances taken, the 

 inhibitory movement in the first trial follows close upon 

 the heels of the instinctive response. Now we know that 

 a wave of excitement once started in the nervous system 

 persists for a certain short time. Hence the inhibitory wave 

 arises before the original excitement has subsided, and as 

 we have seen, impinges on and perhaps modifies or half 

 cancels it in the very first instance. And this modification 

 tends to persist, or at least leave a trace. For we find that 

 as painful experiences are repeated, the original impulse is 

 not merely checked, but sooner or later dies away. This 

 part of the process of learning is therefore suggestive of the 

 fusion of two immediately consecutive waves of excite- 

 ment. If this is what actually occurs in the lowest forms 

 of learning, the element of time would be important, but 

 we may doubt whether it is merely the co-presence of two 

 waves of excitement that is essential. The element of 

 unity we may conceive is the conation which is excited by 

 the sensory stimulus and is inhibited by the painful, 

 insipid, or fruitless result. The effect of this inhibition 

 persists. The special type of conative tendency that has 

 been frustrated, is weakened, possibly cancelled, for a 

 shorter or longer period, while the reverse result happens 

 if the conation should succeed. It is the conation which 

 furnishes the unity to successive acts and explains how it 

 is that a result, supervening when sense excitement is 

 over, nevertheless appears to modify corresponding sense 

 excitements in the future. Be this as it may, in the 



But, in point of fact, the two processes do at times (as some of the above 

 instances show) give evidence of themselves in action. We really get 

 occasionally something like a blend or an alternation. Mr. A. A. 

 Schaeffer has shown that with the frog avoiding habits might be formed 

 in both ways. In some instances a disagreeable object is first taken into 

 the mouth and then rejected. In other cases it is eaten without any 

 effort at rejection but subsequently refused (J. A. B., 1911, p. 324). In an 

 experiment with newts described by Mr. A. M. Rees (J. A. B., 1912, p. 191) 

 we find various intermediate stages. One newt seized and half swallowed 

 a piece of filter paper but disgorged it. It then swallowed a piece of filter 

 paper soaked in meat juice, afterwards disgorging the paper. Two days 

 later it followed and snapped at a roll of yellow cloth, but after once seizing 

 it, refused to follow it again. It seized and immediately disgorged a piece 

 of black cotton, and then refused to follow a piece of white paraffin. 

 " Usually after snapping at the tasteless object a few times the animals 

 refuse to follow any longer, but in such cases they would nearly always 

 follow and try to seize a piece of raw meat of the same size." 



