KELATIVE STIMULATING EFFICIENCY OF LIGHT 153 



a frequency of interruption of 10 per second was next tested and 

 was found to be about equal to that of continuous light, for the 

 average angle made was +12.8 degrees, about the same as that 

 made in two beams of continuous light of equal illumination. 

 Tests in light of flash-frequencies of 5 and 2 per second were 

 next given. The angles of deflection made were 1.4 and 23.4 

 degrees, respectively, showing that the stimulating efficiency of 

 intermittent light of these flash-frequencies was less than that 

 of continuous light. 



Consequently, the reactions of this individual indicate: (1) 

 that intermittent light of a flash-frequency of 20 per second has 

 a higher stimulating efficiency in Vanessa than continuous light, 

 i.e., a given amount of intermittent light has a greater stimulating 

 effect than the same amount of continuous light, (2) that inter- 

 mittent light of flash-frequencies of 5 and 2 per second has a lower 

 stimulating efficiency than continuous light, and (3) that the 

 stimulating efficiency of intermittent light of flash-frequencies 

 of 100, 60, 50, 40, 30, and 10 per second is approximately equal 

 to that of continuous light. These conclusions are in general 

 strongly supported by the results of all of the tests made which 

 are presented in tables 3 and 4. 



By referring to table 3 it will be seen at once that the results 

 presented in the last two columns show that the efficiency of 

 intermittent light of low flash-frequency (5 and 2 per second) is 

 clearly lower than that of continuous illumination. Only in 

 two individuals was there any indication of an exception to this; 

 "H" and "C" both deflected less toward intermittent light of 5 

 flashes per second than they did toward continuous light of the 

 same illumination. In all of the other flash-frequencies the vari- 

 ation in deflection in different individuals is so great that the 

 meaning of the results is not immediately evident. For ex- 

 ample, in specimen F the greatest stimulating efficiency appears 

 to have been at 100 flashes per second; in B at 50; in L at 40; in 

 J at 10; in C and in E at 30; and in N, I, G, and H at 20. A 

 thorough analysis of these results shows however that in spite 

 of this variation the results are quite clear. Such an analysis is 

 presented in the last line in table 3 and in table 4. 



PSTCHOBIOLOGY, VOL. II, NO. 2 



