THE RELATIVE STIMULATING EFFICIENCY OF 



CONTINUOUS AND INTERMITTENT LIGHT 



IN VANESSA ANTIOPA 



WILLIAM L. DOLLEY, JR. 

 From the Biological Laboratory, Randolph-Macon College, Ashland, Virginia 



CONTENTS 



I. Introduction 137 



II. Methods 144 



III. Orientation in continuous light from two sources 147 



IV. Variation in reactions to light 149 



V. Relative stimulating efficiency of intermittent and continuous light. . . T51 



VI. The relation between stimulating efficiency and the ratio between the 



duration of the light and dark periods of intermittent light 159 



VII. Influence of mechanical stimulation and previous experience on the 



reactions of Vanessa to light 166 



VIII. Summary 172 



I. INTRODUCTION 



Many investigators have studied the effect of intermittent 

 light on the human eye, while but few have investigated its ef- 

 fect upon other eyes. In the work on the human eye the fol- 

 lowing four questions have been prominent: 



1. Does intermittent light of high flash-frequency have the 

 same stimulating efficiency as continuous light? 



2. What is the flash-frequency at which the " flicker" of 

 intermittent light becomes imperceptible? 



3. What is the shortest perceptible time interval between two 

 flashes of light? 



4. What is the comparative apparent brightness of a given 

 light acting for various lengths of time? 



The first of these questions concerns Talbot's law. This law 

 has been stated by Helmholtz (1896, p. 483) as follows: 



If any part of the retina is excited with intermittent light recurring 

 periodically and regularly in the same way, and if the period is suffi- 



137 



P8TCHOBIOLOGT, VOL. II, NO. 2 



