Makch 19j 1915] 



SCIENCE 



417 



To look at the matter from another point 

 of view, the present state of our knowledge 

 would seem to indicate that the typical re- 

 flex of our text-books, the unconditioned 

 reflex, is a congenital mechanism. The 

 neurones concerned and the collateral con- 

 nections of afferent and efferent limbs are 

 bom with us. It may require practise to 

 bring the mechanism into perfect working 

 order ; but practise does not produce a new 

 neurone nor have we any reason for think- 

 ing it can produce collateral connections 

 which were not already laid down by hered- 

 ity. The nervous element in locomotion is 

 a case in point. The colt walks from the 

 moment of birth; a human baby not until 

 its second year, and then only after arduous 

 trial and effort; but this does not mean 

 that the nervous mechanism is congenital 

 in the one case and acquired in the other; 

 it merely means that the congenital nervous 

 mechanism is in complete working order 

 at birth in the colt, while in man either 

 embryological development is not complete 

 until later or else use is required to make 

 congenital synaptic connections efficient. 

 Despite the immemorial antiquity of the 

 expression ' ' learning to walk, ' ' it may well 

 be questioned whether any child really 

 learns to walk; whether the facts observed 

 are not equally well explained on the theory 

 that the child finally walks simply because 

 at last the embryological development of 

 its nervous mechanism of locomotion is 

 complete, as is that of the colt at birth; 

 and that the improvement which appar- 

 ently results from its efforts is in point of 

 fact merely the record of the progress of 

 ontogenetic development. 



"With learning to talk the case is entirely 

 different. Here there is no inherited mech- 

 anism leading to a uniform result in all 

 individuals of the species. One child learns 

 to speak English, another German, another 

 Russian ; and if the English child had been 



taken after the first few months of its life 

 to Russia and heard nothing but Russian, 

 it would have learned to speak Russian as 

 perfectly as it actually learned to speak 

 English while growing up in its native 

 country. In this case heredity has fur- 

 nished a nervous system capable of ac- 

 quiring just such associations as those de- 

 scribed in Pawlow's experiments; we are 

 dealing with a process in every way com- 

 parable to the conditioned reflex. 



Finally, if the distinction between con- 

 ditioned and unconditioned reflexes upon 

 which Pawlow insists is correct, some old 

 statements which take us back to our very 

 introduction to the study of physiology 

 need revision, or at least more accurate re- 

 statement. When we speak of "habit being 

 an acquired reflex" we really mean an ac- 

 quired conditioned reflex. There is no rea- 

 son for assuming that the reflex acquired 

 by the repetition of volitional acts is the 

 typical reflex arc; indeed there is every 

 reason for believing the contrary. Paths 

 of conduction become blazed between dif- 

 ferent lower centers because they are si- 

 multaneously excited in the volitional execu- 

 tion of an action, and a mechanism is 

 acquired of whose nature we know next 

 to nothing, but through which the act 

 can be performed more and more easily 

 with less and less conscious effort — or, in 

 physiological language, with less and less 

 participation on the part of the higher 

 centers of the cerebrum. We are not con- 

 cerned with the psychology of this phenom- 

 enon, much less is this the place for specula- 

 tion as to the physiological mechanism in- 

 volved. We are simply concerned with its 

 classification as a distinct thing from the 

 ordinary unconditioned reflex. 



Perhaps when introducing this discus- 

 sion of reflexes I laid undue emphasis on 

 the role of consciousness in the acquisition 

 of conditioned reflexes. In the examples 



