SENSITIZATION BY ANNULAR SURROUNDS . SENSITIZATION AND DARK ADAPTATION

Westheimer has shown that the rod threshold at the center of a 45′ adapting disk can be lowered by adding light in the surrounding annular region. He has also shown that a similar sensitization effect does not occur for dark adaptation curves; that is, dark adaptation curves measured on bleached fields of different diameters appear to be identical. The present investigation confirms Westheimer's finding for dark adaptation curves traced downward to the absolute threshold, and extends it to the case of dark adaptation curves traced downward against real light backgrounds of various illuminances. © 1969.