Theory and Measurement of Visual Mechanisms

Abstract

IOn comparing monocular and binocular critical points for visual flicker, within the fovea, it was found by Sherrington (1902, 1904, 1906) that for similar phases of interrupted illumination fa]Hng synchronously on each retina there was very little reinforcement, so that the binocular fusion frequency was almost the same as when using one eye (or a little higher). The observations were made at a comparatively high flash intensity, and thus at a high flash frequency, save for some incidental tests. No mention was made of differences in critical flash frequency for the right and left eyes of an observer; such differences are always revealed by systematic tests, in our experience, although at the upper end of the F-log I contour they may not be easy to detect.Sherrington's data and the conclusions he drew from them, involving other phase relations in the interruptions of light to the two eyes, are frequently referred to in connection with the general problem of "binocular summation;" doubtless others have noted similar findings; but the basic question seems not to have been carefully re-examined. It has never been made entirely dear just in what respect such observations should be expected to reveal evidence of "summation," and in default of a theory of the flicker response contour naive expectations might very well be obscure. In now making a re-investigation of the relations between monocular and binocular flicker thresholds a chief point has been to establish under opticaUy simple conditions the relation of the binocular flicker response contour to that obtained for each eye taken separately. This has not heretofore been done. It is necessary also to have quantitative information as to the variability of such measurements. Relatively complete contours must be obtained for each eye taken separately before any real discussion of "binocular summation" can be attempted. It cannot be

Evaluating Letter Recognition, Flicker Fusion, and the Talbot-Plateau Law using Microsecond-Duration Flashes

“…Using white-light flashes and varying flash duration across a range from 10% to 90%, i . e ., from 100 ms to 900 ms per one-second interval, Crozier & Wolf [ 12 ] found the flash intensity required to produce fusion was increased as the percentage of light in the duty cycle was increased. This means that persistence of flash influence is longer with shorter-duration flashes.…”

The temporal window of individuation limits visual capacity

“…Estimates of the temporal resolution of vision come from a variety of different tasks but can be divided into two groups of temporal limits: a fast group that operates on the order of 10s of milliseconds and a slower group of visual mechanisms taking more than 100 ms ( Holcombe, 2009 ). The fast temporal limits are usually explained by temporal integration of low-level visual features (like in the case of flicker fusion or integration masking; Crozier and Wolf, 1941 ; Kietzman and Sutton, 1968 ; Scheerer, 1973a , b ; Di Lollo and Wilson, 1978 ; Coltheart, 1980 ; Enns and Di Lollo, 2000 ; Breitmeyer and Öğmen, 2006 ). In contrast, slower temporal limits are usually associated with high-level processing in an object-based frame of reference like in the case of feature conjunctions across space (color-shape: Holcombe and Cavanagh, 2001 ; or orientation-location: Motoyoshi and Nishida, 2001 ) or consolidation of objects in visual working memory ( Gegenfurtner and Sperling, 1993 ; Vogel et al, 2006 ).…”

Evaluating the Talbot-Plateau law

“…From this he concluded that Talbot-Plateau integration was accomplished at the level of the retina. Crozier and Wolf (1941) re-evaluated the issue and supported Sherrington’s position. Shevell et al (1992) have taken the opposite view, providing evidence for a cortical basis for contrast and assimilation of brightness using dichoptic stimulation.…”