Experiments were performed to determine whether it is possible to discriminate which eye or eyes are being stimulated by a point source of light in a dark room when the subject is unaware which eye, if any, is occluded.

There were two stimulus conditions, (a) a continuous source of light, and (b) a flash. The results show that in these conditions discrimination is faulty and, in some instances, at chance level, although there is considerable individual variation. The implications of these results for the argument from transfer, as applied to after-effects, and the theory of depth perception are considered.