22 



HOW WE SEE 



in order to change the visual threshold. 

 Thus, it appears that ultra-sonic vibrations 

 (47), ultraviolet light (44), radio waves (90), 

 and the geographical latitude of the labora- 

 tory where tests are made (50), affect rod 

 sensitivity. 



These reports are so insistent and the 

 claims so positive that they have attracted 

 some attention in certain quarters. Un- 

 fortunately, studies which have been done 

 on this problem in non-Russian laboratories 

 do not confirm the Russian claims. Serrat 

 and Karwosky (81), for example, report that 

 auditory stimulation produced no effect on 

 the general or specific color threshold. 

 Thorne (87) also reports a few incidental 

 measurements on the effects of auditory 

 stimulation on the just perceptible bright- 

 ness of flashes of light 0.0001 seconds in 

 duration. His findings appear to show that 

 the effects of auditory stimulation may 

 either increase or decrease the visual 

 threshold. The changes are small, however, 

 and do not exceed 0.3 log units. 



The most direct experimental evidence on 

 the validity of the Russian claims comes 

 from experiments by Rose and Schmidt (76), 

 Matthews and Luczak (65), and Chapanis 

 et al. (9). Rose and Schmidt studied a 

 great variety of factors — caffeine-metrazol, 

 muscular exercise, strychnine, ultrasonic 

 vibrations, ephedrine, octin, stimulation of 

 taste with saccharin, and Vitamin A in an 

 oil solution and in an emulsion — which are 

 supposed to affect dark adaptation. Their 

 results are well summarized by the state- 

 ment, "When the experiments were carefully 

 made, and the results analyzed critically by 

 the statistical method, none gave convincing 

 evidence that night vision has been im- 

 proved or impaired." These findings are 

 at variance with those obtained by Matthews 

 and Luczak, who report that light muscular 

 exercise increases dark adaptation. The 

 magnitude of the effect depends on which 

 of their data are taken as the control 

 data. In any case, the maximum possible 

 effect amounted to 0.65 log units at 11 



minutes after the onset of dark adaptation 

 and decreased thereafter. Matthews and 

 Luczak conclude that the effects "are not 

 nearly as great as those described by him 

 [Kekcheyev].^" The study by Chapanis 

 et al. made use of a variety of smells, tastes, 

 sounds, and pressures applied to the back 

 of the hand. These authors conclude that 

 "The results of all experiments are com- 

 pletely negative. None of the stimuli 

 used in this experiment either facilitated or 

 inhibited dark adaptation, contrast sensi- 

 tivity, or form discrimination at low 

 illuminations." 



It is difficult to reconcile these conflicting 

 findings. The situation is especially difficult 

 because the Russian reports are extremely 

 skimpy in presenting data or details of 

 apparatus or experimentation. In their 

 article, Chapanis et al. advanced some 

 hypotheses to account for the discrepancies, 

 but the problem cannot be considered 

 settled. It would be highly instructive to 

 obtain a full account of the methods and 

 data of the Russian experiments.^ Without 

 this information, it appears unfikely that 

 further experimental work on this problem 

 at the present time would contribute 

 anything of value. 



The fact that any stimulus — real or 

 imaginary, adequate or non-adequate — seems 

 to produce changes in visual sensitivity in 

 the Russian laboratories makes their results 

 highly suspect. As a purely practical 

 matter it must be recognized that men in 

 military situations are constantly being 

 stimulated by sounds, smells, pressures, 

 internal stimuli, etc. Under these circum- 

 stances — assuming for the moment that the 

 Russian findings are valid — one might 



1 Author's insert 



2 It may be of interest to report that the writer 

 attempted to obtain this information in 1943 

 through military and diplomatic channels. These 

 attempts met with no success. Somewhat more 

 recently (December, 1947), he again attempted 

 to communicate directly with Dr. Kekcheyev 

 via the mails. The letter was returned unopened 

 from Moscow. 



