268 REPORTS ON THE STATE OP SCIENCE. — ^1916 



general text-books are content to introduce fatigue in the most cursory 

 manner, and the student can obtain from them httle idea of the pro- 

 blems which now demand attention.^ Dr. Myers, in Chapter xiv. of 

 his ' Text-book of Experimential Psychology,' Vol. I., has recently 

 made a welcome step in the right direction. 



The results of industrial investigation have now clearly indicated 



" It is worth while to present a brief analysis of the way in which even 

 such an authority as Kuelpe introduces Fatigue into his well-known Outlines 

 of Psychology. After defining a sensation as a simple conscious process 

 standing in a relation of dependency to particular nervoue organs, he states 

 that sensations are compared by means of ' sensible discrimination,' and are 

 experienced and communicated by ' sensitivity ' which may be either direct or 

 indirect (pp. 31 and 33). Sensible discrimination and sensitivity are improved 

 amongst other things by a greater degree of attention and expectation : habitua- 

 tion facilitates attention and expectation, but too great habituation nullifies 

 their effects and dulls the subject's interest in the experiment. 



Practice in a process increases delicacy of perception and readiness of 

 judgment by increasing attentional concentration and capacity of reproduction. 

 Fatigue decreases all these things. Both practice and fatigue may be general 

 or special (p. 43). 



Peripherally excited sensations (p. 87) are of various kinds — cutaneous, 

 tactile, olfactory, visual, and organic. There are also ' common sensations ' 

 in which one or more of these are compounded ; and' there is the eensation of 

 giddiness which may be the function of a particular sense organ, the static 

 sense. The common sensations include hunger and thirst, tickling, itching, 

 and shivering ; cardiac and respiratory sensations, the sensation of being ' all 

 right,' and finally the sensations of exertion and fatigue (pp. 146-148). 



Centrally excited sensations, all of which have previously been peri- 

 pherally excited, are reproduced (through the mediation of direct or indirect 

 recognition and association) modified in various degrees in memory and in 

 imagination. This reproduction, like sensitivity and sensible discrimination, 

 is conditioned by attention, by practice, and by fatigue, general and special. 

 Relaxation after a sleepless night weakens memory in all departments. Per- 

 sistent occupation with a particular object fatigues the memory. Kuelpe 

 (p. 212) regards it as uncertain whether fatigue influences associability and 

 reproductivity directly, or only indirectly — i.e. by way of attention. The 

 abnormal increase of central excitability at a certain stage of fatigue (evidenced 

 by vivid dreams, multiplication of illusions, &c.) seems to indicate that the 

 diminution of associability and reproductivity resulting from fatigue does 

 not affect the central sensations themselves so much as the arrangement, con- 

 nection, and direction which are normal to them under the guidance of 

 voluntary attention. An analysis of the influence of practice leads to a similar 

 conclusion. We must therefore suspend judgment upon the question whether 

 practice and fatigue are conditions of centrally excited sensations co-ordinate 

 with attention. The forgetfulness of old age is probably to be explained by 

 reference to fatigue (p. 217). 



Affective states, the pleasantness and unpleasantness of a sensation, are 

 adversely influenced by fatigue, which (p. 261) weakens wliat would otherwise 

 be a pleasure, and increases what would normally be a moderate unpleasantness. 



Fatigue is apt to retard the work of auditory analysis (p. 303). It ia 

 far more difficult to distinguish the individual tones in a clang or to reduce 

 a compound clang to its simpler constituents when the mind is fatigued than 

 when it is fresh. The effect of fatigue, therefore, seems to be restricted to 

 the increase of fusion degree, to the reinforcement of the unitariness of the 

 total impression. Fatigue also diminishes the accuracy of estimating time 

 intervals, brightness contrast, and : 



Fatigue lengthens reaction time in experiments. 



Though there is a relation between fatigue and sleep, sleep can hardly be 

 regarded as a special instance of the general phenomenon of fatigue, as it 

 is often impossible imder circumstances of extreme exhauetion. A theory 



