April 7.. 192 1] 



NATURE 



l;83r 



The Galvanometric Measurement of Human Emotion.^ 

 By Dr. A. D. Waller, F.R.S. 



"\17'E are all of us familiar, subjectively within our- 

 '"' selves, objectively by the behaviour of our 

 neighbours, with the signs and symptoms of emotion, 

 and with the fact that such signs and symptoms are 

 more or less under voluntary control and can be sup- 

 pressed or simulated at will. We are moved to or 

 from an object we may desire or fear. We are moved 

 to laughter or to tears by events witnessed and 

 imagined; and whereas all men are moved in the 

 mass by the same general motives of light and dark, 

 food and hunger, love and hate, we know by everyday 

 experience that no two men react in identical fashion 

 to the same motives. 



1. Physiologically, all emotions are expressed as 

 neural outbursts from the central nervous system 

 through efferent nerves to muscles and glands; emotion, 

 in general, results in intensified physiological activity 

 at the periphery of the body — muscles and glands, heart 

 and blood-vessels, the face and eyes and skin. A 

 movement of surprise, a palpitation of the heart, a 

 blush, a pallor, a shiver, a rush of tears, a dilated 

 pupil — all these and other signs of emotion consist in 

 sudden local intensifications of the chemical exchanges 

 that are in constant operation between the living cells 

 of the body and the fluid medium by which they are 

 surrounded. We know indeed that all such chemical 

 exchanges are controlled through efferent nerves, and 

 we speak of this control as their trophic action, but 

 we are scarcely prepared at the present day to recog- 

 nise the close association between signs of emotion 

 and the phenomena of nutrition. 



2. The physical sign of emotion is known to psycho- 

 logists as the psycho-galvanic reflex. It was first 

 definitely revealed to us twelve years ago • by 

 Veraguth,' of Zurich, and has since then formed a 

 favourite subject of study by many later observers 

 whom I shall not attempt to enumerate. I joined in 

 the hunt four years ago,* and was very quickly 

 satisfied that this physical sign affords the most 

 convenient possible gauge and measure of human 

 character and of human temperament, seeing that it 

 declares hoixt much a given subject is moved by his 

 thoughts and feelings. A spot of light showing the 

 movements of a galvanometer connected with the 

 palm of the hand exhibits the fluctuating emotions 

 of the person to whom the hand belongs, and if the 

 person be an ordinary normal person it is only the 

 palm of the hand, and not any other part of the skin 

 of the upper extremity, that shows the response. 

 My first point is, then, that the emotive response is, 

 ^ar excellence, a palmar phenomenon, and I shall, 

 as my first and chief experiment, undertake to demon- 

 strate this point. (Experiment.) 



3. Mr. X. Y. has been good enough to lend himself 

 to my purpose. His hand and his forearm are con- 

 nected with each of two galvanometers and two 

 Wheatstone bridges. The round spot belongs to the 

 hand circuit, the square spot to the forearm circuit, 

 and balance can be adjusted in each circuit separately 

 by suitable manipulation of the two resistance boxes. 

 In bofli cases the wiring is such that increased con- 

 ductivity of the hand or of the forearm gives move- 

 ment of the spots to my right, i.e. any emotive 



1 A discourse delivered at the Royal Institution on February 4. 

 ,,^*^ Psychogalvanische Reflexphenomen." ^Berlin, 1900.) 

 » "The Galvanometric Measurement of 'Emotive' Physiological 

 Changes." Proceedings of the Royal Society, B, vol. xc, p. 214, 1917. 



NO. 2684, VOL. 107] 



impulses from the brain down motor nerves to the 

 hand or to the forearm will cause deflection to the 

 right. Let us watch the two spots for a while. I 

 expect you to see that the hand spot behaves ir- 

 regularly, whereas the arm spot creeps steadily across 

 the scale without showing any of the vagaries of the 

 round spot. 



You realise now why I have been at trouble 

 to show the simultaneous behaviour df two 

 spots. With only the hand in circuit of one 

 galvanometer you should at first have felt doubtful 

 whether the movements you saw were really due to 

 emotive discharges, and not to otherwise imper- 

 ceptible muscular twitchings such as are perceived 

 and utilised by thought-readers. It would otherwise 

 have been desirable to set up some very delicate 

 form of myograph to satisfy this doubt. I shall show 

 you presently, by asking the subject to make a least 

 possible movement of one of his fingers, that the 

 round spot — i.e. that indicating the electrical resist- 

 ance of the hand — shows a deflection which is due 

 to a minute disturbance of contact, and, therefore, 

 takes place in the direction opposed to that of 

 an emotive response. I am sure you will realise with 

 me what a mercy it is that the deflection by slight, 

 often quite unavoidable, movement is, in general, the 

 contrary of that of the emotive response. 



4. But to return to our experiment. The subject is 

 at rest; both spots are reasonably steady, but by 

 reason of his past experience he knows that an evil 

 moment is approaching. As you may see by the 

 irregular movements of the hand spot, he is beginning 

 to worry, making a picture in his mind of the pain 

 he is about to undergo by steel or fire, and, obviously, 

 this disturbance of quietude creates a condition that 

 is not favourable for recognising or measuring the 

 disturbing effect of any real interference with his com- 

 fort. The emotive effects of my threatening language 

 must be allowed to subside. You cannot expect to 

 study rings made by throwing a stone into a pond 

 unless the pond is quiet; you must wait for it to get 

 still. When he comes to rest Mr. X. Y. will react 

 smartly and obviously in response to the suddenly 

 threatened pin-prick or to a real pin-prick. (Trials by 

 pin and matches. Real and imaginary pin-pricks and 

 burns.) 



You now, perhaps, feel fairly well satisfied 

 that the statement made a few minutes ago is cor- 

 rect. In the upper limb of a normal person emotive 

 responses to .slight excitations are confined to the 

 palm of the hand. The only other part of the bodv 

 in which they occur is the sole of the foot, but this 

 I shall ask you to take on trust; it really is not 

 necessary that the actual evidence should be brought 

 into court. It would merely be a repetition of what 

 vou have just witnessed; and this lantern-plate 

 (Fig. i) will, after all, afford us the quickest, as well 

 as the most conclusive, evidence. 



^. I shall venture to trespass just a little further upon 

 Mr. X. Y.'s endurance to make good one further 

 point, although it is a point that you mav already 

 have noticed. 



This palmar emotive response is, in mv view, to 

 be regarded as caused by a sudden augmentation of 

 electrical conductivitv in a membrane or membranes 

 in the fourth arm of the Wheatstone square. That 

 augmentation of conductivity is to be understood as 



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