Size contrast as a function of conceptual similarity between test and inducers

In four experiments, the effect of the semantic relationship between test and inducing stimuli on the magnitude of size contrast in an Ebbinghaus-type illusion was explored. In Experiments 1 and 2, the greatest illusion was found when test and inducing stimuli were identical in shape and differed only in size. Decreased size contrast was found when inducing stimuli were drawn from the same category as the test stimulus, but were not visually identical. Even less size contrast was found when inducing stimuli were from a near conceptual category, with the least effect when they were drawn from a completely different category. In Experiment 3, it was demonstrated that even if test and inducing stimuli are drawn with identical geometric elements, the size contrast illusion is greatly reduced if they represent apparently different conceptual categories (through the manipulation of orientation and perceptual set). In Experiment 4, any geometric or spatial confounds were ruled out. These results suggest that size contrast is strongly influenced by the conceptual similarity between test and inducing stimuli.     

Visual acuity in children as a function of hue

Ninety-six suburban school children, 7 to 14 years old, were tested, with colored parallel bars as acuity targets, to assess relative effects of hue, age, and intelligence on visual acuity. The main effects of color and age were found to be significant but with no significant interaction. A one-way analysis of variance for each color indicated blue and black acuity improved with age while red did not. Since natural myopia for blue light may have accounted for the effect with blue, a second experiment was undertaken with focusing being introduced as a variable. Focusing eliminated the effect of age, but the color effect remained significant. Lowest resolution thresholds were obtained with black, next red, and blue highest. There was no relationship between acuity and intelligence nor were there any sex differences.     

Block-design performance as a function of hue and race

The block-design subtest of the WISC was presented in two forms, the standard red/white and an alternative blue/yellow, to two groups of fourth- and fifth-grade children. Twenty black children and 20 white children performed the red/white task with no significant differences between their scores. Another 20 black and 20 white children performed the blue/yellow task showing a significant interracial difference. Within the group of black children there was also a significant difference between the red/white design scores and the blue/yellow design scores. It is proposed that genetically determined differences in the pigmentation of the fundus oculi account for these results.     

Size of test patch and simultaneous contrast

Two experiments were done to find the effect on simultaneous brightness contrast of placing test patches in, as against outside, the fovea. When the display was magnified so that the test patches were outside the fovea no statistically significant effect was found. Very short exposures, to eliminate eye movements, did not appear to reduce contrast.     

Amount of surround and test-inducing separation in simultaneous brightness contrast

Simultaneous brightness contrast is investigated in the fovea as a function of (1) amount of surround of the inducing field (Experiment 1) and (2) separation between the test and inducing fields (Experiment 2). Circular test and match fields subtending 14 min (radius) are used throughout. The inducing field, held constant in area, is a circular annulus (615 sq min) varying from a quadrant on one side of the test circle to an annulus completely surrounding the test circle. Test-field apparent brightness is not significantly affected by amount of inducing-field surround when the separation between centers of the test and inducing fields is held constant (Experiment 1). Experiment 2, though, shows that apparent brightness increases significantly as the separation between the centers of the test and inducing fields is increased.     

Experimental measures and theoretical account of hue scaling as a function of luminance

Functions relating the magnitude of chromatic response to stimulus luminance were determined at the unique green and yellow wavelengths. These measured functions were used to account for the shift from a preponderance of green at low stimulus luminances to a preponderance of yellow at higher luminances, for a stimulus wavelength of 550 nm. The two hue magnitude functions were found to have the same power-law exponents, and the hue shift was due to the difference in thresholds between the two opponent-color systems.     

Size contrast as a function of figural similarity

Size contrast occurs in numerous configurations where a test figure appears apparently larger when surrounded by small elements and apparently smaller when surrounded by large elements. Using the Ebbinghaus illusion, the magnitude of this effect is shown to vary as a function of apparent similarity between test and inducing element.     

Border contrast as a function of retinal locus

When the visibility of a small test spot was measured by direct brightness matching at various locations along the white edge of a black and white border, it was found that the white background was perceived as becoming progessively brighter as the border was approached. The effect was greater when a corner was neared. Moreover, greater effects, i.e., larger differences between the edge effect and base level (no border) were found at distances farther removed from the fovea (0 deg 12 min to 3 deg 52 min).