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The Pamphlet Collection of Sir Robert Stout: Volume 78

The Measurement of Mental Fatigue

The Measurement of Mental Fatigue.

The following extract is reproduced from the 'Journal of Mental Science' for July, 1906:—

Among the characteristics which we agree with Kraepelin in regarding as the essential mental features of the personality, varying degrees of capacity for acquiring skill by practice and of liability to fatigue are by far the most important. The effects of practice and fatigue on the course of mental work are such as absolutely to determine the amount that can be done and the mental capacity for work. They differ, however, in their relation to the amount of work done, not only in the antagonistic direction of their effects, but also in other features which clearly show their kinship with the corresponding phenomena on the physiological side. While the effect of practice hardly ever extends beyond the sphere of the work that has been practised, and acts on other functions, even of a similar nature, only in a limited degree, fatigue has a far more extensive effect and reduces the general mental capacity for work. There is much in the common experience of daily life which seems to contradict this statement. Thus, change of work seems to have a favorable influence on our working capacity when we are fatigued. This appearance has led even eminent physiologists to assume that fatigue acts within the same narrow limits as practice. Thus, Mosso says, in his book on 'Fatigue': "Apparently fatigue is localised in a particular region of the brain, for we often see that people who have become incapable of thinking over a certain subject, or considering a particular piece of business, find relief in thinking about something else, or free themselves from the sense of dulness in their heads by fixing their attention intently on other and different things—for instance, on a game of chess." Richter, too, ascribes a restorative effect to change of work in education, and thinks that he has thus discovered why school children do not show more fatigue.

These assumptions are, however, founded on an error. Weggandt's experiments on the influence of change on continuous mental work have revealed the fact that the fatigue produced by any particular mental work affects other kinds of mental activity, even when they are qualitatively different, and that the effect of one kind of work or another does not depend on their psychological similarity, but purely on the amount of fatigue produced. . . . .

There are also other respects in which fatigue differs essentially from practice, When, for instance, we cause anyone to add up a series of figures of one place for about ten minutes every day for several days together, we observe that the amount of work done from day to day increases considerably at first, but that after a few days the difference in amount becomes very small, and, indeed, is hardly perceptible. From this we see that skill or practice increases rapidly at first, but that after a comparatively short time it reaches a degree beyond which its growth is very gradual. Fatigue, on the other hand, increases continuously from its very first beginning, and, finally, unless it is checked in time by intervals of rest, passes into a state of exhaustion, in which mental capacity for work is completely annihilated. . . . .

Within the sphere of education it is the question of over-pressure in schools which is most closely connected with that of fatigue. The numerous investinga- page 93 tions that have been made within the last few dozen years, especially from the educational point of view, have shown that the demands made by schools in the present day on the children who attend them go far beyond all permissible bonds. . . .

It is obvious that the solution of the problem of over-pressure is one of the most important tasks of practical pedagogics. . . . .

Kraepelin has already pointed out that when fatigue is increasing the feeling that the work is growing harder often drives the worker to a fresh exertion of his strength. . . . .