PSYCHO-PHYSICAL INVESTIGATIONS WITH THE GALVANOMETER AND PNEUMOGRAPH IN NORMAL AND INSANE INDIVIDUALS
CHAPTER 2: THE PHYSICS AND PHYSIOLOGY OF THE PSYCHO-PHYSICAL GALVANIC REFLEX
So far as has yet been determined, it would seem that the sweat glandular system is the chief factor in the production of this electric phenomenon, inducing on the one hand under the influence of nervous irritation a measurable current or, on the other hand, altering the conductivity of the current. Since water contact excludes changes induced by pressure on metal electrodes, and blanching of the fingers by the Esmarch bandage excludes changes in connection with the blood supply, both of these factors play but a small part in the deviations of the galvanometer. Change in resistance is brought about either by saturation of the epidermis with sweat, or by simple filling of the sweat-gland canals or perhaps also by intracellular stimulation; or all of these factors may be associated. The path for the centrifugal stimulation in the sweat-gland system would seem to lie in the sympathetic nervous system. These conclusions are based upon facts at present to hand and are by no means felt to be conclusive. On the contrary, there are features presented which are as yet quite inexplicable,2 as for instance, the gradual diminution of the current in long experiments to almost complete extinction, when our ordinary experience teaches that resistance should be much reduced and the passing current larger and stronger. This may possibly be due to gradual cooling of the skin in contact with the cold copper plates. This can be obviated by warm water contact or by resting the copper plates upon warm sand bags. Yet there is still an inviting field for investigation here.
If, when the hands are placed upon the copper-plate electrodes, they be pressed down more firmly, there is a slowly-increasing deviation of the galvanometer, but only to a minor degree. If the area of contact be diminished by the raising of the fingers or by lifting of the palms, there is a sudden diminution in the amount of current, marked by sudden reduction of amplitude in the excursion of the light.
FIG. 1. Curve to show effects of deep inspirations and coughing upon the galvanometer.3
A deep inspiration alone, or a deep expiration, without alteration in the contact of the hands, increases the deflection of the galvanometer, while ordinary respiratory movements do not affect it. Coughing also causes a considerable rise in the galvanometric wave. We are inclined, to think that this rise in inspiration and expiration, and with coughing may also be psychic, that is, emotional. Certainly in the curve we observe exhaustion by repetition of the command to cough or breathe deeply, as in the case of other analogous stimuli. The deviations brought about by altered contact by deep inspiration and expiration, and by coughing, are all readily recognised after some experience, and are readily differentiated from those depending wholly upon psychic influences. Warm hands naturally permit a larger current than cold hands. The level of the curve rises when the skin in contact grows warmer or moister, and descends with increase of coldness in the skin (see fig. 1).
Expectation.―As soon as the galvanometric experiment begins, and the circuit through the test person is closed, there is a rather rapid rise with some fluctuation of a curve induced by expectant attention. Tarchanoff was much struck by this. Attention is, as Bleuler  has pointed out, nothing more than a special form of affectivity. Attention, interest, expectation, are all emotional expressions. The extent of this expectation curve rises in normal individuals, depending upon their varying degree of affectivity. Expectation is not only manifested at the beginning of an experiment in the galvanometer curve, but may be observed throughout the experiment in connection with every stimulus, sensory or verbal. It is particularly strong in connection with the threat of pricking with the needle, or threat of letting fall a heavy weight. The influence of expectation on the curve becomes less with each repetition of the same series of stimuli, and seems to disappear wholly with indifferent stimuli; while, with the threat stimuli just referred to, which are more lively and actual, repetition may diminish the curve, or at times increase it if the test case is uncertain whether the threats in the repetition are to be a real prick of the needle or an actual fall of the weight. In beginning an experiment, we therefore wait until the first influence of the emotion of expectation has subsided.
Emotion.―Excluding the affect of attention, we find that every stimulus accompanied by an emotion causes a rise in the electric curve, and directly in proportion to the liveliness and actuality of the emotion aroused. The galvanometer is therefore a measurer of the amount of emotion and becomes a new instrument of precision in psychological research.
Imagined emotion.―The amount of deflection seems to stand in direct relation to the actuality of the emotion; but, as Tarchanoff pointed out, the presentation of an emotion already outlived to the imagination does deviate the galvanometer, such deviation depending naturally upon the facility of the test person in living over the old emotion in his imagination. The following experiment, tried upon one of the writers, is an illustration: The list of stimuli was placed before him, while the reader of the deviations called off at intervals Nos. 1-2-3-4-5-6, allowing time for concentration upon the idea, and for the rise and subsidence of the wave. Between the periods of concentration on the emotional images, the test person allowed his eyes to wander indifferently about the room, and his mind to run on in different objects seen.
An Experiment in the Deflection of the Galvanometer in Imagined Conditions.
Series of stimuli used.―A series of stimuli, sensory and verbal, strong and indifferent, intellectual and emotional, was arranged and tested upon numerous normal individuals, besides which word associations were used in connection with the galvanometer. In some of the experiments the test person was in an adjoining room, the electric connections and signals being easily adjusted for this purpose.
The following is the series of stimuli:―
The verbal stimuli were varied to a slight degree with various individuals, to adapt them to different conditions and circumstances, but the general character of the stimuli was the same.
Here, too, the relations are somewhat obscure, which may be owing to the occurrence of very few altered reproductions. Only half of the above numbers coincide with our expectations.
These stimuli were ordinarily repeated three times in each individual, normal or pathological, and subsequently the series of word stimuli were given for the word associations, these were also repeated once or twice. From seventy curves, fig. 2 (H., nurse, Series III) is selected as a general illustration of the galvanometric curve.
Fig. 2. Galvanometer and pneumographic curves in a normal person (H., a nurse). The numbers at the top of each stimulus line correspond the the series of nineteen mixed stimuli printed in the text. 2 and 2a represent two falls of the weight occurring between 13 and 14 instead of between 1 and 2 in this curve, which was the second repetition of the series. Between 10 and 11 someone entered the laboratory.
This man was emotional and in the third series here presented the curves and more rounded than in the first and second series. At the same time they serve to show the character of the emotional curve. Stimuli 3, 4, and 5, although they were but simple multiplication, induced an emotional curve because H. was a nurse and was embarrassed in doing mental arithmetic before experimenters. Stimuli 8, 9, and 10 were practically exhausted in this third trial and show very little. Between 10 and 11 someone entered the room. The weight was let fall twice between 13 and 14 instead of at 2, and being unexpected produced a large and a smaller wave of alarm. The threatened needle at 14 and threat of fall of large leaden weight at 15 still produced large waves, and show how strongly actuality in an apprehension influences the curves. Again, at 18 the enquiry if his wife was pretty, she being far from so, induced a lively emotion and correspondingly high wave, for this question was here a surprise as well, not having been asked in the preceding series.
Fig. 3. Repetition of same stimulus questions in a normal person (H. a nurse) three successive times to show gradual exhaustion of emotional wave in the galvanometer curve. In 3rd series question 1, someone entered the laboratory and caused an extra wave.
Exhaustion of stimulus by repetition.―When the first series of stimuli is recorded, the curves are usually characterised by abrupt ascent and descent with rather sharp summits. The curves diminish in size and the summits
FIG. 4. Here G., a nurse, is asked about a quarrel with another nurse, H. The fluctuation galvanometer waves 21 and 22 represent the wavering emotions aroused.
become more rounded by each repetition, showing a slower excitation and slower reaction of the emotion. This is well illustrated in fig. 3, where several curves induced by the same stimuli in the first, second, and third series in the same individual are reproduced. Wave No. 1 in Series I also exhibits in the descent the fluctuating character of an emotion which is slowly and waveringly passed off. This is even better shown in fig. 4, from Case G., who was asked questions calculated to produce a complex emotional state such as the galvanometer perfectly indicates. In quite a number of instances the heights of the waves of the three successive series were measured and the following two illustrations are selected as examples of the differences in height (in millimetres) of the curves of the stimuli in the three series. Waves were selected which had not been affected in any of the series by interruptions, change of contact, coughing or deep inspirations.
Table 1, Case of H. Diminishing Excursions of Galvanometer in Successive Stimulations.
Table 2, Case of G. Diminishing Excursions of Galvanometer in Successive Stimulations.
Note.―In the averages of these two tables the eleventh column of figures was not included as the emotion of expectation that the weight would really be dropped modifies especially the second trial, while in the third trial there was less of such expectation.
In these tables the falling off of the height of the emotional curve was very well shown, and in both the livelier affects produced even in repetition by actual threats of the needle and weight are typical. In Series II of the first table the threat with the weight raised the curve to over fifty-nine because the trial person thought that the weight would actually fall in this experiment, whereas before it was a threat only.
Latent time.―It was noted by Tarchanoff that the galvanic wave began to rise from one to three seconds after a stimulus was given. We have verified this period time in all normal conditions, but the latent time varies with different people and at different times. In the curves that we have thus far taken we could not well complicate the apparatus with a chronograph adjustment, and have estimated the space of latent time in a number of normal cases by measuring the distance of the curve from the moment of stimulation to the beginning of ascent of the emotional curve, taking the measurements in millimeters. The kymograph drum revolved slowly. The following results were obtained. Nurse B. with the series of mixed stimuli given above showed in the first series an average of 2.06 millimetres; the repetition of the second series averaged 2.55 millimetres; with Nurse G. and the same series of mixed stimuli in Series I the average was 1.85, in the second 1.76, and in the third or final series 2.32 millimetres. Dr. P with the same series showed an average latent period in the first trial of 3.15, and in the repetition an average of 4.40. Dr. R. with the same series had an average period in the first trial of 4.05 millimetres, and in the second trial of 4.50 millimetres. In a series of word associations Dr. R. showed at first an average period of 2.95 millimetrers, and in the repetition immediately after the average was 4 millimetres. With word associations Nurse H. showed in the first series an average latent period of 2.26; in the repetition or second series the latent period was increased to 3.55, and with a third trial of the same words the latent period had become 4.14. These figures with regard to the latent period show therefore that with repetition there is an increase of the latent period of time simultaneously with the rounding off and diminishing amplitude of the curve, both corresponding with exhaustion of the power of the stimulus. We were unable to determine in this investigation that there was any marked difference in latent time in relation to the various forms of stimulation whether physical or psychic, and when psychic with or without answer to questions or words, though such differences will probably be discovered by further experiment directed to this end.
Normal individual variations of galvanometer curve.―We find considerable difference in the curves made by the galvanometer in normal persons. In some the waves are of rather small and even excursion, corresponding to the unemotional or phlegmatic nature of the test person. In others there is wide excursion, with fluctuating or bifurcated waves, rapid ascents and descents, expressing great emotional lability. These normal variations are illustrated in figs. 5 and 6.
Fig. 5. Dr. R., normal curve with rather indifferent word association stimuli. Unemotional type.
With a stop watch we estimated that the time of revolution of the drum was 4.55 millimetres in five seconds. Hence the latent time in the above normal individuals was about as follows:
2. On one occasion with three persons in the circuit and one Bunsen cell, the sudden fall of a weight with loud noise caused a deflection of two centimetres.
3. All tracings except figs. 9, 14, 15, 18, have been reduced to one eighth their size.