Evidence against independent processing of black and white pattern features

Following adaptation to a rectangular grating, subjects observed a shift in the perceived duty cycle of a test grating (Burton, Nagshineh, & Ruddock, 1977; DeValois, 1977). This suggests that size information about black and white pattern components may be analyzed independently. We have tested this hypothesis by combining adaptation to a 2-cpd rectangular wave grating (narrow white bars and wide black bars or vice versa) with adaptation to a 4-cpd sine wave (narrow white and black bars. The data do not support the independent analysis of white and black components, but they may be accounted for by mechanisms sensitive to the relative phase relations among the spatial frequency components of the input.     

Attention,brightness contrast,and assimilation: The influence of relative area

A model of information transmission in the visual system which describes the effect of attention on apparent brightness is examined. This model states in part that the luminance of the portion of the visual field which captures the attention is overweighted in arriving at an overall average luminance level across the visual field. As this average must be computed with respect to both luminance and relative area, it is hypothesized that increasing the relative area of the portion of the visual field that captures the attention will result in a greater effect on the apparent brightness of all parts of the visual field. Two predictions, which involve the effect of relative area on apparent brightness, are experimentally tested and confirmed.     

Raster versus calligraphic display devices for assessing visual performance: The influence of stimulus area and uncertainty

Sixty-hertz raster scan monitors provide relatively inexpensive solutions to problems associated with presenting complex visual stimuli. However, they restrict the user to displays in which stimulus characteristics cannot be changed more often than once every 16.67 msec. Calligraphic monitors allow very high frame rates, but not the generation of complex or chromatic images (unless very expensive monitors are purchased). A method is reported for increasing the frame rate of some raster monitors at the expense of the number of lines that are painted. Also, data relating to the influence of such a modification on visual performance is presented.     

Gray-scale graphics using dot matrix printers

Gray-scale graphics can be printed on conventional dot matrix printers by varying the dot density, rather than the dot intensity. The technique described here takes advantage of the high-contrast print possible with these printers and the increased resolution available using compressed character sets. The reflectance of individual characters and symbols was measured with a photometer, and a character set was selected that increased from dark to light in equal logarithmic steps of reflectance. Various criteria for choosing dot patterns are discussed, and the technique is applied to two-dimensional visual field maps.     

Inferences about mechanisms that mediate pattern and flicker sensitivity

Attention, Perception, & Psychophysics - Visual sensitivity to a flickering, sinusoidal grating was assessed in multiple sclerosis patients and control observers. It was found that losses in...     

The effect of texture oil the magnitude of

The magnitude of simultaneous brightness contrast was measured while the coarseness of the textural overlay was varied. Remits from 10 Ss indicate that as the size of elements in the texture increases, the amount of obtained contrast decreases. An interpretation of these results in terms of the spread of lateral inhibitory effects is offered.