Concerning with dark adaptation, a number of experiment has been made in which e.g., the duration of preadapting period and the level of intensity to which the eyes are exposed during that period have been varied. In most of these experiments, the matter of concern has been exclusively the measurement of the threshold, i.e., the measurement of the photosensitivity. In this case, rhodopsin (the photosensitive substance in the retinal rods) decompose into transient orange, visual yellow and visual white by light, and these are regenerated into rhodopsin (visual purple) in dark. The change of sensitivity in various conditions based on such physiological foundation, of course not only by that reason, may have some influence on visual perception, especially recognition of figure, geometrical illusion, figural after-effect, and so on, because I think that to fixate some figure implies to adapt the field which have a gradient of brightness. Therefore, by studying the relation between photosensitivity and figural after-effect, I think that we can explain the mechanism of the rise and the characteristics in figural after-effect. Still more, through following up the photosensitivity and extending it to the investigation of relation between photosensitivity and the various phenomenon in visual perception, I think that we can explain the foundamental mechanism of some visual processes. So that, as the first step, I am taking the experimental aproach as to the relation between photosensitivity and figreal after-effect.
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