Effect of Differential Adaptation of the Eyes upon Threshold Sensitivity*

Experimental determination was made of the effect of intense light adaptation (6.20 log Trolands) of one eye upon the dark-adapted threshold of the other eye. A psychophysical method derived from Békésy and analogous to the “up and down” method of Dixon and Mood was used. Three subjects showed a slight increase in sensitivity; one showed no change. The change was not statistically significant for the group. The finding is consistent with the accepted view that the states of adaptation of the eyes are independent and in contradiction to studies which have found an averaging effect.