16 



SCIENCE 



[N. S. Vol. XXXI. No. 784 



The resting brain is probably normally 

 during life in a state of neural tension iu 

 more or less stable equilibrium. An effect- 

 ive stimulus disturbs this equilibrium and 

 the precise effect will depend upon variable 

 synaptic resistance or neurone thresholds 

 which change with different functional 

 states of the organism as a whole and of 

 the brain in particular. If this activity 

 involves the cerebral cortex of a human 

 brain, it may be a conscious activity, the 

 kind of consciousness depending on the 

 kind of discharge. But the consciousness 

 must not be thought of as localized in any 

 cortical area. 



The discharge in question may rever- 

 berate to the extreme limits of the nervous 

 system and the peripheral activities may 

 be as essential in determining the conscious 

 content as the cortical. Indeed, we have 

 considerable evidence that many of our 

 conscious acts take their most distinctive 

 psychic cpalities from the "back stroke," 

 or reverberation of a neural discharge from 

 the periphery back to the cortex. 



Thus far we have tacitly assumed that 

 consciousness is an integral part of the 

 complex of bodily functions. This assump- 

 tion lies at the basis of most modern work 

 in the field of comparative psychology 

 and rests on the thoroughly scientific basis 

 of a large body of observation and infer- 

 ence. In the nature of the case demonstra- 

 tive proof is impossible, for consciousness 

 as I know it is a purely individual experi- 

 ence; but without the assumption that like 

 behavior in other men implies experience 

 like my own in similar circumstances the 

 science of psychology can not go on, and 

 without the further assumption that other 

 animals have like experience in proportion 

 as their behavior is like my own compara- 

 tive psychology is an impossible science. 



Now keeping in mind the dynamic con- 

 ception of the workings of the nervous 



mechanism developed above, let us see 

 whether the introspective examination of 

 some very simple conscious reaction can 

 be put into scientific relation with other 

 biological processes, or whether it must be 

 left out of our science in the cold isolation 

 of mere epiphenomena and similar meta- 

 physical abstractions. 



An unfamiliar or unexpected sensation 

 is experienced; let us say a noise. There 

 is a moment of hesitancy while the sensory 

 stimuli, numerous awakened memory ves- 

 tiges, each perhaps with its own emotional 

 coloring, and many half-formed impulses, 

 surge in consciousness. When the prob- 

 lem presented by the new situation is 

 solved, the mental tension is relieved and 

 the intellectual process crystallizes at once 

 into action. I am thinking about it no 

 longer: I have got an idea; and the ap- 

 propriate act follows immediately and au- 

 tomatically unless inhibited by some extra- 

 neous influence. Here we have an active 

 and complex interplay of conscious ele- 

 ments corresponding to what in the ob- 

 jective manifestation we called the antic- 

 ipatory phase of the reaction, and the 

 conscious process comes to an abrupt end 

 as soon as it passes over into the already 

 stereotjrped form of reaction. That is, 

 t]iis conscious pi-ocess ends, though of 

 course it may be followed at once by 

 another similar chain of events. 



Here we see how intelligence and feel- 

 ing are developed as the servants of action. 

 They do not appear so long as the action 

 can be effected without them and they 

 vanish as soon as the reflex machinery of 

 an adaptive action is set in motion. Con- 

 scionsness is a functional phase of the 

 more complex mechanism of those higher 

 non-stereotyped actions for ivhich the 

 reflex machinery is inadequate, in nvtich 

 the same way that the tropisms of Para- 

 mecium and the sucking reflex of an in- 



