The Variation of Visual Sensory Reflex Action with Intensity of Stimulation*

Intermittent Stimulation by Light

“…For their two untrained observers the points are irregular; but they seem to show a slope of about 9.0. Allen's (1926) measurements give a slope of 8.6 for yellow light of 570 m~, which on the basis of general experience, may be considered the same as for white light. Thus most observers record values between 9 and 12, with a preponderance of 11.…”

“…All these peculiarities of slope disappear when a small field is used. Allen (1919Allen ( , 1926 has in general confirmed the work of Porter and of Ives, but has differed from them by drawing through his measurements about five short straight lines of different slope instead of the usual two. In our estimation, the data presented by Allen do not justify this treatment; the points appear to lie on a continuously curving line.…”

Time order error in successive judgments and in reflexes. I. Inhibition of the judgment and the reflex.

“…There is evidence from many studies that, without practice, a shift in the intensity of Si may cause inhibition to go over into facilitation. Allen, for example (1), has reported that a stimulus applied to the left eye produced 'reflex' effects on the critical flicker frequency of the right eye, and he has shown that the nature of these effects is dependent on the stimulus intensity, so that a wave length which at high intensity produced enhancement, might at a lower intensity elicit depression. Dodge, too, has discussed this point at length (4, p. 69), quoting Frohlich to the effect that "Inhibition is nothing but weak excitation."…”

The relationship of the size of the surrounding field to visual acuity in the fovea.

“…It may be noted here that the ranges of these sets, being determined in part by the astigmatism of the eye, frequently did not overlap. Any reading which deviated as much as 2.5 A.D. 1 from the mean of its set of five was discarded, an error of that size being considered the result of factors which this experiment was not intended to measure. The readings were scanned as soon as a group was completed and if it appeared likely that one would be thrown out, an extra was taken at the time.…”

“…On the other hand, attempts at theoretical formulation of the visual process have so far failed to be completely satisfactory, perhaps because none of them has adequately included the factor of the surrounding field. Even in the restricted field of the photosensory process, the most valuable formulation, that of Hecht ( 23), fails at more than one point to account for the data; and the importance of the omission from his equation of any term descriptive of the condition of the retina outside the area tested is 1 The writer is indebted to Professor Robert T. Ross and to Professor Walter R. Miles for guidance during the course of this experiment and for valuable criticisms and suggestions in the preparation of the manuscript.This work was submitted to the faculty of the Graduate School of Yale University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.…”