Intensity of light and area of illuminated field as interacting factors in size of pupil.

Abstract

This experiment aimed to show the influence of the size of the illuminated field or the size of the stimulus on size of pupil. The results are as follows: (1) Size as well as brightness of field affects the size of the pupil. In considering the effect of intensity of light on size of pupil we have thus always to take into account the size of the illuminated area as well as the intensity of its illumination. (2) Within the range of size and brightness of field used, change in the brightness of the field exerts a greater effect on the size of the pupil than change in the size of the field. (3) There is a fairly close correspondence in the effect of change of brightness of field on size of pupil for each of the sizes of field employed. (4) Similarly there is a correspondence in the effect of change in size of field on size of pupil for each brightness used, but in this case the correspondence is not so close. (5) Increase of size of field not only has a great deal of effect on size of pupil, but the percentage effect for a given ratio of change in size is greater through that part of the field for which there is an increased sensitivity to light, at least in dark adaptation, than it is for the more centrally located portions of the field. (6) The effect of change of size of field on size of pupil is not proportional to the total amount of light emitted or reflected from the field for the range of variations used in this experiment. (7) The knee of the curve for size of pupil plotted against brightness of stimulating field occurs for one observer at about 9.25 ml and for another at 6.45 ml and for a third at 11.57. (8) There is no pronounced knee in the curve showing size of pupil plotted against size of field for the range of variations used in this study. (PsycINFO Database Record (c) 2006 APA, all rights reserved)