KRAEPEL1N ON PSYCHOLOGICAL 
EXPERIMENTATION IN PSYCHIATRY. 
AUGUST HOCH, M. D. 
McLean Hospital, Waverley, Mass. 
Reprinted from the 
American Journal of Insanity 
for January, 1896. KRAEPEL1N ON PSYCHOLOGICAL EXPERIMENTA- 
TION IN PSYCHIATRY. 
BY AUGUST HOCH, M. D., 
McLean Hospital, Waverley, Maes. 
During the first half of this year an aiticle appeared by Kraep- 
elin, in which this author gives a summary of some of his work in 
psychiatry, of his efforts to make “ the psychological experiment ” 
applicable to psychiatry. Owing to the importance of this subject, 
a short review may be of interest to the alienists of this country. 
Perhaps a few preliminary remarks, however, will help to put the 
work in its proper light, and will show the standpoint from which 
the author views the study of mental diseases. 
It is well known that for many years anatomical studies have 
taken a prominent place in investigations by those who deal with 
mental diseases, a fact which, from the history of psychiatry and 
medicine in general, is easily explained. These studies, with which 
many illustrious names are intimately associated, have brought 
forth many brilliant results; at the same time normal anatomy of 
the nervous system and the study of nervous diseases have derived 
the greatest benefit from these efforts, while the share which fell to 
psychiatry is, after all, very small. A knowledge of the anatom- 
ical relations of the nervous system, however, and an inquiry into 
the structural alterations, are absolutely necessary for a scientific 
study of mental diseases. But it is certainly a mistake to think, as 
many apparently do, that with this the work could be done; that 
the task of psychiatry lies solely in a pathology of the brain cor- 
tex, for we must certainly admit with Kraepelin that a pathology of 
the brain cortex, no matter howT far advanced it may be, will never 
give us an insight into abnormal mental phenomena as such. As 
he says, in the introduction to his excellent text-book: “ This would 
only be possible if the brain secreted ideas and emotions as the 
kidney secretes urine;” or, in other words, if an exact knowledge 
of the cerebral mechanism should include also a knowledge of 
psychical processes. “ But nobody will deny,” he continues, “ that 
we could have a comprehensive knowledge of the finest molecular 
processes of the brain without having the remotest idea that we have 
before us the organ of psychical life. This is fundamentally differ- 
erent from the materialistic views which wre find more or less con- 2 
sciously expressed in many text-books and articles, even of the 
present day, in this and in other countries. In regard to the 
dependence of the psychical on the physical we know nothing more 
than that a relation exists, and a correlation of the two parallel 
lines, the abnormal mental phenomena and the anatomical (or chem- 
ical) changes, must, of course, be the final aim of a scientific study 
of mental diseases. That, in spite of many theories, the actual steps 
in this direction are very few, nothing shows better than the diver- 
sity of these theories. It follows, therefore, that it is necessary to 
approach the subject from two points of view, with equally accu- 
rate methods, namely, from the somatic and the psychical; and cer- 
tainly mental diseases have primarily a psychical side to them, and 
it is by a study of their psychology that we have, above all, a chance 
to arrive at an understanding of the relations of mental symptoms 
among each other, and of their genesis, and to trace back compli- 
cated to more fundamental phenomena. But the advance of psy- 
chology has been rather neglected by alienists, in spite of the fact 
that the last decades have brought this study into line with the 
natural sciences. This circumstance, as well as the scarcity of 
actual facts, and frequently a leaning to a one-sided anatomical con- 
ception, have brought forth innumerable theories, so that no field of 
medicine is so full of hypotheses as psychiatry. The need of a 
sound psychological basis, therefore, and the need of having reliable 
methods, as in the other branches of natural science, which allow 
us to go deeper than simple observation can go, have led Kraepelin 
to make use of experiments which, thanks to the work of men 
like Ernst Heinrich Weber, Fechner, and particularly Wundt, 
have proved so valuable in normal psychology. 
It is well in this connection to quote from the last paragraph of 
the article we are about to review, where Kraepelin says that it is 
time that, instead of indulging in deep speculations and ingenious 
inventions, we should go to work at a serious and conscientious 
investigation, advancing step by step; that we need facts and 
not theories, which latter have only a right to exist inasmuch as 
they allow of the formulation of problems, giving thus a starting 
point for the application of accurate methods to new investigations. 
In what manner such work maybe begun, what are some of the 
problems which can be formulated, what has already been 
achieved, how much preparatory work is necessary, and, finally, 
from what different aspects experiments may be made valuable for 
the difficult study of mental diseases — all this forms the contents of 3 
the article which is entitled: “ Der psychologische Versuch in der 
Psychiatric.* It forms the introduction to a series of publications 
to be issued at irregular intervals, in which Kraepelin wishes to 
put on record the studies done in his laboratory in the field indi- 
cated in the above title. 
Before Kraepelin others have entered this field of work and have 
made some experiments of this kind, but nevertheless it is he who 
must be considered the first one who followed this line of study 
with a definite aim and with a logical sequence. He not only 
applied methods which were used in experimental psychology, but 
devised new ones particularly fitted for the investigation of 
abnormal conditions; and it is well to say at the beginning of this 
review that the objections which could be made to a study of this 
kind — namely, that experimental psychology is itself not enough 
advanced to be applied, and that it is questionable whether the 
methods there used are applicable to abnormal individuals—do not 
hold good, since Kraepelin takes (the methodsffesslfrom physiological 
psychology than the experimental method in general. 
Besides the valuable aid which Kraepelin expects, and has in part 
already obtained, from the study of normal individuals with refer- 
ence to pathological conditions, he hopes by experimentally investi- 
gating the latter to arrive at an analysis of mental diseases which 
is more accurate and complete than could be gained by simple 
observation, and it is significant of the manner in which the work 
has been done that many years (since 1883) were spent chiefly in 
studying normal, or artificially produced abnormal, conditions, in 
order to test the method, and to lay a foundation before investi- 
gating pathological conditions. This is, after all, the only proper 
manner in which to approach such a subject; and it is this same 
careful spirit, coupled with an exceedingly clear and unbiased 
objective judgment, which strikes us so forcibly in all the writings 
of Kraepelin, and in the article before us not less than in his other 
works. 
In a short introduction, Kraepelin, speaking of the rapid develop- 
ment of experimental psychology, expresses his surprise at the 
fact that, in spite of the importance which this branch certainly has 
for the psychiatrist, the latter paid comparatively little attention to 
it. He dwells upon the difficulty of the subject, on the care which 
has to be taken in experimenting, which not only consists in collect- 
*Peychologische Arbeiten. Edited .by Emil Kraepelin, professor of psychiatry in 
Heidelberg. Leipzig, 1895, Engelmann. ing a vast number of observations, but the most difficult part of 
which is to be found in the interpretation of the results. 
A chapter of twenty-one pages on methods follows. Here the 
question is raised, where shall a study like this begin? The meth- 
ods most thoroughly investigated in physiological psychology are 
difficult to apply to patients, and we must endeavor to obtain chiefly 
such as make less demand upon the person experimented upon, and 
are more like every-day occurrences; methods, furthermore, which 
do not require complicated apparatus, and not too long a time for 
experim entation. 
In the field of reaction-time others have worked before Kraepelin, 
but inasmuch as these observers frequently failed to obviate the 
well-known faults of the chronoscope as an apparatus working by 
means of electro-magnets, their results are often doubtful. Never- 
theless, studies in this field are by no means unfit for the purpose in 
view, if the patients are carefully selected. By interposing, more- 
over, between the elements of a simple reaction, other acts, as 
choice between different movements, associations, and the like, an 
insight can be obtained into these as well as, to a certain extent, 
into that particular element of a simple reaction which is altered, 
as the latter is in itself a complex act. Such studies of association 
times, together with other studies, have already led to some impor- 
tant results in the interpretation of a common symptom in mania 
and other affections. It had been thought that the incessant talking 
of such patients, the linking of superficial associations (or rhymes), 
which constitutes the “Ideenflucht” of the Germans, was due to a 
quickened association-time — that associations called up each other 
more rapidly than normally. The opposite has been shown to be 
true, and the whole symptom proves to be an outcome of the gen- 
eral motor excitement in which the motor processes of speech take 
their part.* 
Among the methods originated by Kraepelin are the so-called 
continuous methods, in which in a given time as large a number 
of simple tasks must be solved as possible; thus, e. y., the adding 
of units. (Appropriate books with figures have been printed for 
this purpose.) At a signal made by a clock striking every five 
minutes, a sign is made in the book. The amount of work done in 
such periods can be counted and compared. Other tasks can be 
4 
*Cf., also, Aschaffenburg: “Ueber Ideenflucht,” paper read at the XIX. Wanderversamm- 
lung der sfidwestdeutschen Neurologen und Irreniirzte in Baden-Baden. Arch. f. Psychiatric 
und Nervenkrankheit. Vol. XXVI, 1894, 597. 5 
set — reading, memorizing senseless syllables (Ebbinghaus), or 
columns of figures, etc. In this manner we are able to study not 
only more or less simple psychical acts with particular reference to 
their duration, but also, which is of the greatest importance in this 
connection, the changes which occur during the work, and which 
are due to fatigue and practice and the like. Reading and writing 
can be investigated along lines already started. Moreover, studies 
have been made on the sense of touch by an appropriately arranged 
method, which allowed an insight into fatigue and centrally pro- 
duced sensations in this domain. The sense of time, purely motor 
functions, and the depth of sleep, are other fields which have been 
looked into, and which promise much interest. All the methods 
which Kraepelin gives have not been mentioned here. Besides 
these, new ones can be devised, but yet all need first a thorough 
study with normal individuals, and a comparison by means of exact 
measurement in order to be certain of their applicability.* 
An experiment in the best sense is one in which we can produce 
the particular condition which we wish to study, and in which we 
can not only alter it at will, but control some of the modifying con- 
ditions. Applied to the study of mental disease, this would mean 
the production artificially and intentionally of a mental disturbance. 
Although the application of this method must needs be very lim- 
ited, it is nevertheless what the author attempts; indeed, he heads 
his second chapter: “Artificial Mental Disturbances.” 
To study the patients experimentally at the height of their 
disease is usually impossible; in the beginning of it they are, as a 
rule, not accessible to us, but during convalescence we may be 
able to obtain information through experimentation; nevertheless 
the former would be the most important, namely, the study of the 
first stages. And here it is possible, within certain limits, to pro- 
duce the conditions under which deviations from the normal 
develop. In the first place the variations in our psychical state 
produced by the daily changes of external conditions must, in this 
connection, be considered and analyzed. They will be within nor- 
mal limits, but we may fairly expect to be able to recognize by a 
study of them, the general lines along which pathological conditions 
become developed. Of these daily alterations there are two factors 
which first suggest themselves — fatigue and practice — but as soon 
as we go into the practical investigation of the question we find it 
*Cf. former works: “Ueber die Beeinflussung einfacher psychischer Vbrgange dutch 
einige Arzneimittel.”—Jena, Fischer, 1892. Also “Geistige Arbeit.”—Fischer, Jena, 1894. 6 
complicated, resolving itself into many smaller ones. Thus, with 
reference to the former, the effects of fatigue should be studied 
when it is produced in a rested organ, on the one hand; on the 
other hand, when it is brought on in an already fatigued one. 
Bodily fatigue and mental fatigue should be investigated sepa- 
rately, and the influence of the one on the other be studied; more- 
over, the influence of external conditions, like nutrition, sleep, etc. 
The r61e which over-exertion of any kind plays in the produc- 
tion of mental diseases is well known. Although we can not pro- 
duce, experimentally, serious disturbances of this kind, neverthe- 
less, here also, as was said, it may be hoped to get an insight into 
the direction along which these influences act; and a study of this 
kind may aid us to analyze, possibly, more complex mental dis- 
turbances, and we may be able to separate the essential from the 
non-essential. 
Well aware of the impression which such statements will be apt 
to make on those who are not familiar with the subject, Kraepelin 
says that he is prepared to have this looked upon as “ a castle in 
the air,” “ and certainly,” he says, “ we are very far from our goal;” 
but, on the other hand, there are also some results already obtained. 
Aschaffenburg made studies on the effect of exhaustion. He 
experimented for a whole night. We all know we feel different 
after a long night’s work. But only by appropriate experiments 
was it possible to analyze this. There was chiefly a more difficult 
reception of external impulses. There were centrally produced 
sensations (hallucinations), a prolonged association-time. The 
associations were, moreover, more stereotyped, more superficial, as 
we find in the “ Ideenflucht ”; and, finally, the central motor excita- 
bility was greater.* Kraepelin notes in this the striking resem- 
blance to an exhaustion psychosis, and draws attention to the fact 
that if we had to analyze a collapse-delirium we would come to 
the same conclusions. Since, in the latter condition, similar causes 
act and produce it, there is more than a merely superficial, outside 
similarity between the two conditions. 
Another field for experimentally produced mental disturbances 
is to be found in some of the intoxications. Kraepelin’s studies on 
the action of alcohol have led him to a better understanding of the 
mental disturbances ensuing from its use. The chronic intoxica- 
tions can be better understood, and, moreover, it is just this study 
* Cf., also, Aschaffenburg: “ Die psychischen Erscheinungen der ErschOpfung,” paper read 
at the Wanderversammlung in Baden-Baden. Arch. f. Psych. Bd. S5, 1893; 595. 7 
which has led him to his present opinion on “ Ideenflucht,” and to 
the understanding of mania. The action of ether has been shown 
to be very similar to that of alcohol. Similarly of cocaine, and yet 
some differences have been observed, whereas morphine has been 
found to be quite different in its effects. Other drugs have also 
been examined. The study of all of them has not only a direct 
bearing upon our clinical experience with such intoxications, 
but also it gives us methods to study slight deviations from the nor- 
mal mental conditions, and will aid in this way our understanding 
of other abnormal as well as normal conditions. 
The drug effects, known up to the present time, as far as they 
have been measured, can be traced back to two fundamental activ- 
ities of our psychical life, namely, to the reception and working 
out of impressions, and to the transmission of will-impulses; and 
the whole variety of action of the different drugs — alcohol, ether, 
chloroform, amylnitrite, chloralhydrate, paraldehyde, tea, and mor- 
phine— may be attributed to the varied combinations of accelera- 
tion or slowing of these two phenomena. Unquestionably the 
view obtained thus far is one-sided; and we must, by further 
inquiry, by formulating new questions and devising new methods, 
gain a more comprehensive view. 
There is one consideration of which Kraepelin speaks in this con- 
nection which, problematical as it may yet seem, can not be passed 
over in this review. As we said above, the correlation of psy- 
chical alterations and physical ones has made very little progress. 
And how could it be otherwise? On the one hand there is no sharp 
observation of clinical facts; on the other no marked anatomical 
changes have been observed in the nervous tissue. In the latter 
an improvement is promised by Nissl’s method; in the former, by 
accurate observation helped by experiment. Here the study of 
artificial abnormalities caused by chemical poisons, on the one 
hand, and, on the other, the lesions experimentally produced in 
animals, may lead later to a correlation of the two. 
The third chapter is headed: “Personal Fundamental Peculi- 
arities.” Here Kraepelin comes to a very important part of his 
study, namely, the influence which the individuality of a person 
has upon the development of mental disease. This he estimates 
to be greater than has been supposed, external influence having a 
smaller share than was formerly thought. And although the extent 
of the influence exerted by a factor lately so much discussed, 
namely, auto-intoxication, can not as yet be estimated, there 8 
unquestionably remain enough mental diseases in which there are 
no such circumscribed causes to be found at all, but in which the 
intrinsic peculiarities of the personality are to be made responsible 
for the pathological development. Degeneration, neuropathic 
taint, are terms which express these individual conditions. But 
such terms are vague, and sifting and grouping is necessary. This 
is the task of individual psychology. It is by no means an easy 
one, for we are dealing, not with tangible things, but with processes, 
which are changed and crossed by numerous and incalculable con- 
ditions in the most varied manner. Particularly interesting in this 
connection are the two properties of our psycho-physical organiza- 
tion, fatigue and practice. It was found that the latter was 
apparently different in different functions, while the former seemed 
to be a more fundamental property of the person. Of course in these 
studies many other points were found as these lines were followed 
out. The duration of the influence of practice in different individ- 
uals had to be looked into, and is unquestionably of importance. 
Another property was found which is different from practice itself. 
It is what we call “ getting into the work;” it also increases the 
amount that can be done, but is of a different nature, in that it is 
lost very soon, whereas the effect of practice remains for a long 
time. That practice is nothing else than a special form of memory 
is further not to be doubted. Fatigue, on the other hand, lessens 
our faculty for work, and the amount which we can accomplish, 
but here Kraepelin says a distinction must at once be made between 
fatigue and sense of fatigue’, they are two factors which need not 
by any means go hand in hand; on the contrary the two may be 
quite opposed to each other, a distinction which, in this country, 
has been insisted upon so strongly by Cowles.* Depressed con- 
ditions show frequently a sense of fatigue without fatigue. On the 
other hand, we find in anxious and maniacal patients an absence of 
the sense of fatigue; but fatigue itself may progress to profound 
exhaustion. Finally, Kraepelin thinks we may perhaps partly 
trace back the baneful influence of emotions to the fact that they 
rob us of the sense of fatigue, and hence disturb the necessary 
circle of work and rest. This is the more serious, since probably 
the sense of fatigue represents a necessary pre-condition for sleep. 
Both, therefore, should be compared particularly in our studies 
of psychopathical individuals. Just as in practice the duration 
of its effects must be studied, so here in fatigue the time for 
+ Shattuck Lecture, 1891, Boston Medical and Surgical Journal. 9 
recovery, and with it possibly the depth of sleep, should be investi- 
gated. 
Finally, a most important factor is the influence of distraction, or, 
rather, our power to resist it. This is our power of concentration. 
The importance of it need not be dwelt upon. To possess means 
for the measurement of this would be a valuable addition to psycho- 
pathological methods, but little has been done in this direction. 
We see from these points which have been selected, that here quite 
a number of personal fundamental properties have been found, 
which not only may be studied, but which, as experiments have 
shown, actually can be studied. The study consists in the finding of 
the rapidity with which different processes occur, be it in the domain 
of perception of external impression, in the association of ideas, or 
in the transmission of will impulses. 
The fourth chapter is headed, “Psychical Status Bracsens.” In 
these psycho-physical properties, which, as has been seen, include 
neither feeling nor anything referring to the contents of our think- 
ing, but are directed to the formal portion of our psychical life, to 
its dynamics, we have to deal with essentially psycho-physical factors. 
Although only a beginning of these studies has been made, a con- 
tinuation may lead to a more accurate analysis of personalities and 
individual peculiarities than has been done before; above all, each 
step forward is made by experimentation, and reveals facts. In such 
studies methods will have to be devised, and tried thoroughly on 
one normal individual. The factors which appear to be the most 
important must be separated out, and must be studied by as short 
methods as possible on numbers of individuals. On the other hand, 
we must strive in the studies of individuals to get as many tests as 
possible to apply to them, i. e., methods which give us an insight 
into as many parts of their psychical life as possible, for it is the 
whole individual which we are dealing with. In accordance with 
this plan Kraepelin has attempted, within the limits of the methods 
at his disposal, to establish in a number of persons some of their 
fundamental peculiarities, to obtain a status praesenspsychicus, so 
to speak. This is, of course, as yet incomplete. 
The study consisted of a careful arrangement, on five consecu- 
tive days — on each of which an hour’s work was done — of the 
better developed methods above mentioned, so as to obtain an 
insight into as many psycho-physical properties as possible. But in 
addition to these methods he suggests, finally, others, which in part 
refer to the contents of our thoughts. He had a person write down in five minutes as many nouns as possible, or sensory impressions 
which had a marked color, or things which produced noise, or things 
which were agreeable or disagreeable, or, finally, abstract ideas. 
He thinks that in this way we may get an insight (1) into the nature 
of association, how different associations are connected, what type 
of association is prevalent; (2) into the relative development of col- 
ored or of acoustic memory pictures; (3) into likes and dislikes; 
(4) into the production of concepts. These methods seem perhaps 
rudimentary as yet, and Kraepelin has done little with them, but 
they certainly are very suggestive. 
In the last chapter Kraepelin speaks of the possible value which 
treatment and prophylaxis might draw from experiments as they 
have been indicated. An insight can be gotten, for example, into 
the question why maniacal patients are better treated by baths and 
rest than by leaving them to their constant desire to move about. 
We can get a knowledge of the psychical action of the drugs we 
use; and with regard to the prevention of insanity, we have now, 
through Kraepelin’s studies, a better insight into the action of 
alcohol on mental processes, which it never stimulates, but always 
paralyzes. That steps can further be made toward a proper psy- 
chical hygiene is also evident from what has been said. 
This review has taken much space, yet numerous important and 
interesting points could not be touched at all, f orr which the 
reader is recommended to make a careful study of the original. 
He will find a great number of facts which have been elucidated 
by the studies of Kraepelin and his pupils, and many valuable sug- 
gestions; and on every page he will gain the impression that these 
latter are not based upon vague speculations, but upon a long expe- 
rience in practical, well-directed work in the laboratory. But as 
was said, the original is itself only an outline of the study which 
Kraepelin inaugurated—a study the details of which are partly 
published in former articles, and partly are to appear in the 
Psychologische Arbeiten, which, therefore, I also wish to recom- 
mend to the interest of the American psychiatrist. 
10