MEASUREMENTS OF STRESS 



429 



tions and delusions, semi-dreaming states, 

 depersonalization, double vision, and con- 

 sistent increase of irritability. Experiments, 

 which have run up to 100 hours of sleep 

 deprivation, also showed that in well mo- 

 tivated subjects fatigue and boredom were 

 not usually marked, although irritability is 

 aggravated (3, 73). Diurnal rhythms tend 

 to be preserved. Activity and moving about 

 may be necessary to keep from falhng asleep. 

 (See Section V, 7.) Effects of prolonged 

 sleep loss have been reviewed elsewhere (73) 

 and are considered in detail in another sec- 

 tion of this book (Chapter 15). 



2. Dietary Factors 



While the general topic of diet also is 

 treated elsewhere (Chapter 14) , it may not be 

 amiss to comment on the wisdom of pro- 

 viding for submariners the "best chow in the 

 Navy." There is also evidence that the 

 "open ice box" tradition is a good one, for 

 it appears that a higher and more consistent 

 level of muscular and general efficiency is 

 maintained on five or six meals rather than 

 three meals per day (57). Even mild de- 

 grees of hypoglycemia may lead to impaired 

 performance, while hyperglycemia may help 

 to offset effects of anoxemia. 



Another question concerns nutritional re- 

 quirements under conditions of chronic stress 

 Most workers are agreed that vitamin in- 

 creases above the level obtained in a good 

 diet are not helpful under normal conditions 

 (72), but there appears some indication that 

 vitamin utihzation may be increased under 

 various types of stress. Niacin requirements, 

 for example, may increase with elevation of 

 external temperatures (64, 71). 



III. Measurements of Stress 



A. Expressive Manifestations 



The fact that in emotion organic changes 

 normally facihtative of adjustment to the 

 environment may occur in the relative ab- 

 sence of overt motor activity suggests that 



a need for action may be sensed by the in- 

 dividual notwithstanding that he may be 

 aware of the futility of doing anything about 

 it. In other words the emotionally induced 

 organic changes may be symptomatic of 

 effects within the nervous system. For this 

 reason the outwardly observable signs of 

 emotion have often been referred to as "ex- 

 pressive" (14). Procedures for recording 

 these peripheral changes have been referred 

 to as "expressive methods" (35). Any at- 

 tempt we make to explore the nature of 

 psychophysiological relationships or to de- 

 vise tests of psychophysiological performance 

 imder stress is hkely to employ such ex- 

 pressive methods. 



The number and variety of physiological 

 changes which can be recorded by mechanical, 

 optical, pneumatic, electrical and other de- 

 vices is practically unlimited. In practice 

 what is recorded is determined in part by 

 accessibility of the activity for convenient 

 registration. It may not be assumed, how- 

 ever, that all recordable activities are equally 

 worth registering or that they have the same 

 significance as indices of arousal or emotion. 

 Psychophysiologically the various physiolog- 

 ical measures may have quite different sig- 

 nificance. Among more frequently used in- 

 dicators are the following: 



1. Electromyograms. The muscles have 

 already been considered at some length as 

 the site of symptoms expressive of psycho- 

 physiological "tension" (28, 68) and reac- 

 tion to stress. 



2. The Galvanic Skin Reflex. GSR, an 

 index of palmar sweating, is one of the most 

 valuable and readily used indicators. It is 

 one of the most useful indices of "tension" 

 or "background excitation" (22), particularly 

 so far as the higher levels of the brain are 

 involved. Functionally, as has been pointed 

 out, palmar sweating is represented in the 

 motor region of the cortex and is accessory 

 to manipulative motor processes in a manner 

 analogous to the way in which sahvary secre- 

 tion may be preparatory and facilitative for 



