March 29, 1894] 



NATURE 



505 



J'eire, there has been much animated discussion, into 

 which I do not propose here to enter. Suffice it to say 

 that if we represent by a curve the rise of sensation from 

 the threshold where it first dawns, to its maximum, the 

 law seems to hold good only for the mid-region. Various 

 methods of experimentation are employed. Weber and 

 Fechner employed chiefly the method of tabulating the 

 just discernible differences in sensation, of increasing, 

 that is to say, the intensity of the stimulus, and noting 

 when this increment is just perceptible. Others, using 

 larger intervals, have employed the method of estimating 

 equal increments. Others, again, have constantly doubled 

 the stimulus and noted the change in sensation. In all 

 cases it must be remembered that what we are really 

 dealing with is the perception of the relations between 

 certain given sensations. This is a fact too often lost 

 sight of. We have to infer from these relations the 

 intensity-curve in sensation. 



In addition to experimental investigations concerning 

 the qualities and intensities of sensory elements in con- 

 sciousness, there are others which deal with the feeling- 

 tone, that is, the pleasurableness or painfulness of the 

 sensation. Here with increase in the stimulus there is a 

 rapid culmination of tone to the pleasurable maximum, 

 after which it falls off pretty rapidly, and further increase 

 gives rise not to pleasure, but to pain. 



Researches on the rate of transmission of impulses 

 along the afferent and efferent nerves may be regarded 

 as mainly physiological. Suffice it to say that the rate 

 is about 120 feet per second for ingoing impulses, and 

 about no feet per second for outgoing impulses. 

 Transmission in the spinal cord appears to be less rapid. 

 The results of experimental investigations on the 

 localisation of function in the brain appear to justify the 

 hypothesis that the automatic centres— or the centres 

 concerned in merely organic response — are quite distinct 

 from the control-centres, which are probably restricted 

 to the cerebral cortex. It is a good working hypothesis 

 that the centres which minister to control are the seat of 

 those molecular disturbances which are concomitant with 

 consciousness. Consciousness apart from control would 

 be a mere epi-phenomenon of no practical use to the 

 organism. It is scarcely necessary for me to do more 

 than remind the reader of the conspicuous success which 

 has crowned the efforts of those who have patiently and 

 systematically applied the experimental method to the 

 localisation of the centres of motor control. The motor 

 regions of the hemispheres have now been mapped out 

 with considerable exactitude. The centres of motor con- 

 trol in this region would seem to play down, so to speak, 

 along the specialised channel of the " pyramidal tract," 

 upon the lower automatic centres enforcing or inhibiting, 

 as the case may be, their activity. They would seem to 

 be developed on a secondary arc — the arc of control — 

 superposed upon the lower reflex or responsive arc with 

 its automatic centres. Sensory centres in this arc of 

 control would seem to be, as might well be expected, less 

 definitely restricted in position, as they are also more 

 difficult of investigation. In all this field of research, 

 as in the transmission of impulses, we are experimenting 

 more on the physiological than on the psychological side 

 of psycho-physiology. 



When we come to association, very little that is exact 

 and assured is known of the physiological aspect. It is 

 said that association tracts — that is, groups of fibres con- 

 necting together the several centres in the cerebral 

 cortex — are almost, if not quite, absent at birth, and are 

 established during the development of experience, which 

 may well enough be so ; but what may be the physio- 

 logical conditions of their development, we can at present 

 only guess. On the psychological side much has been 

 written on association ; and in recent times Mr. Francis 

 Galton, followed by Trautscholdt and others, have carried 

 out experiments with the object of estimating the time that I 



NO. 1274, VOL. 49] 



elapses between the reception of a simple impression and 



the occurrence of a simple idea suggested thereby. Such 

 time would seem to be about three-quarters of a second. 

 Much attention has been paid to what is termed 

 " reaction time " ; that is, the time which elapses between 

 a given simple stimulation and the resulting responsive 

 motion. This was found by Lange to vary according as 

 the person who is being tested directs his attention to 

 the expected sense-impression or the anticipated motor 

 response. In the case of a simple response to a visual 

 stimulus, the reaction time in the former case is rather 

 more than one-fourth of a second, but in the latter case 

 only about one-sixth of a second. Practice tends to 

 shorten the time, while fatigue lengthens it. A pre- 

 monitory signal just before the stimulation markedly 

 shortens it. Other experiments have been conducted 

 with a view to ascertaining the time taken in simple cases 

 of discrimination. This, too, varies very much with 

 practice ; and it is questionable whether the shorter 

 time-values measure an act of discrimination properly 

 so called. This part of the subject is full of difficulties 

 in the interpretation of the results obtained. 



In the Harvard psychological laboratory interesting 

 researches have recently been carried out under the 

 direction of Prof. ^Miinsterberg. One of these deals 

 with memory. Experimental results seem to show that 

 a series of presentations offered to two senses at the 

 same time, e.g. to sight and hearing, is much more easily 

 reproduced than if given only to sight or only to hearing 

 — a fact of educational value. Another series of experi- 

 ments deals with the effect of attention. The unexpected 

 result is reached that all stimuli appear relatively less 

 when the attention is from the outset directed to them, 

 as compared with stimuli received while the attention is 

 otherwise occupied, e.g., with simple addition sums. This 

 result and the methods employed in the investigation 

 are likely to undergo criticism. 



Enough has now been said to indicate the kind of 

 work on experimental lines which is being done in psycho- 

 physiology. In England, while valuable researches have 

 been prosecuted in cerebral localisation, comparatively 

 little has been done on the lines which are followed up in the 

 German and American psychological laboratories, though 

 Islr. Francis Galton's valuable psychometric observations 

 have been based on somewhat similar methods. I think 

 that this is a matter for regret. It is true that both 

 methods and results need perfecting and clarifying. That 

 is generally so in pioneer work. It is true that it is 

 mainly to elementary and simple psychological processes 

 that the methods are applicable. But we must begin with 

 the simple, however desirous we may be of reaching a 

 knowledge of the complex. It is true that such experi- 

 mental work cannot take the place of introspective ob- 

 servation. But may it not be used to supplement the 

 older method ? English psychologists have done such 

 good work on the old lines, that one could wish that the 

 newer methods should be given a fuller and more exten- 

 siv^e trial. Somewhat is indeed being done, and there 

 are signs of improvement. We need also systematic 

 work in zoological psychology. Observations which 

 I have made on newly-hatched chicks and ducklings, 

 stimulated thereto by suggestions from my friend 

 Mr. T. Mann Jones, have convinced me that there is a 

 wide field for careful experimental work on the instincts 

 and the dawning phases of intelligence in young animals. 

 We must employ the experimental method if we would 

 make further advance in the study of the mental facul- 

 ties of animals. Is it too much to hope that the time is 

 not far distant when there shall be established in England 

 chairs of zoological and experimental psychology, the 

 occupants of which shall have the direction of adequately 

 equipped laboratories wherein systematic observations, on 

 the lines I have above indicated, may be conducted ? 



C.'Llovd Morgan. 



