Iris Pigmentation and Visual-Geometric Illusions

Perception ◽  
1978 ◽  
Vol 7 (4) ◽  
pp. 473-477 ◽  
Author(s):  
Stanley Coren ◽  
Clare Porac
Keyword(s):  
Retinal Image ◽  
Scattered Light ◽  
Illusion Magnitude ◽  
Ebbinghaus Illusion ◽  
Image Degradation ◽  
Lyer Illusion ◽  
Iris Pigmentation ◽  
Line Elements

Blur or degrading of the retinal image has been shown to be a factor in the formation of visual-geometric illusions where intersecting line elements are present. Light irises allow more scattered light within the eye, which results in more image degradation than found in dark-eyed subjects. Measurements on 755 observers show that illusion magnitude varies as a function of iris pigmentation for a configuration with intersecting line elements (Müller — Lyer illusion), but not for a configuration devoid of such features (Ebbinghaus illusion).

Geometric-Optical Illusions Under Isoluminance?

2017 ◽  
Author(s):  
Kai Hamburger ◽  
Thorsten Hansen ◽  
Karl R. Gegenfurtner
Keyword(s):  
Poggendorff Illusion ◽  
Ponzo Illusion ◽  
Ebbinghaus Illusion ◽  
Optical Illusions ◽  
Magnocellular System ◽  
Lyer Illusion ◽  
System P ◽  
Visual Areas ◽  
Parvocellular System ◽  
Delboeuf Illusion

This chapter briefly introduces nine classical geometric-optical illusions. These include the Delboeuf illusion, the Ebbinghaus illusion, the Judd illusion, the Müller-Lyer illusion, the Ponzo illusion, the vertical illusion, the Hering illusion, the Poggendorff illusion, and the Zoellner illusion. It then demonstrates that they persist under different luminance conditions and under isoluminance. The empirical findings show that our conscious percept is similarly affected by luminance conditions and isoluminance, suggesting that joint contour processing (chromatic and luminance) may extend well beyond early visual areas. The chapter further discusses these concepts in terms of the magnocellular system, the parvocellular system, and the koniocellular system.

Decrement and the Illusions of the Mueller-Lyer Figure

1994 ◽  
Vol 79 (2) ◽  
pp. 707-717 ◽  
Author(s):  
Clare Porac
Keyword(s):  
Perceptual Learning ◽  
Illusion Magnitude ◽  
Group Level ◽  
Illusion Decrement ◽  
Significant Time ◽  
Lyer Illusion ◽  
Significant Decrement ◽  
Level Data

Decrement, a time-related decrease in the magnitude of the Mueller-Lyer illusion, was measured separately for the wings-out and the wings-in variants of the Mueller-Lyer figure. There were significant reductions of wings-out illusion magnitude during the decrement period. Observers viewing the wings-in segment showed a non-significant decrement pattern. Analyses of individual decrement patterns showed that illusion magnitude did not decrease for a number of observers even when there were significant time-related trends at the group level. Data for 80 observers imply that the mechanisms of perceptual learning proposed by previous models of Mueller-Lyer illusion decrement are not sufficient explanations of the decrement process.

Decrement of the Brentano Müller-Lyer Illusion as a Function of Inspection Time

Perception ◽  
1998 ◽  
Vol 27 (2) ◽  
pp. 183-192 ◽  
Author(s):  
John Predebon
Keyword(s):  
Visual Inspection ◽  
Illusion Magnitude ◽  
Inspection Time ◽  
Inspection Period ◽  
Illusion Figure ◽  
Illusion Decrement ◽  
Lyer Illusion ◽  
Time Period ◽  
Post Test ◽  
Time Periods

Two experiments are reported in which the decline or decrement in the magnitude of the Brentano Müller-Lyer illusion was measured. Observers made a pre-test judgment and, after a variable intervening time period, a post-test judgment of illusion magnitude. In experiment 1, the intervening time periods were 1, 2, and 3 min during which time the independent groups of observers allocated to each of the three time periods either systematically scanned the Brentano figure (inspection conditions) or waited until the intervening period had elapsed (no-inspection conditions). Experiment 2, which included an additional 5 min intervening time period, evaluated a response-bias explanation for the results of the inspection conditions of experiment 1. Taken together, the findings of the two experiments indicate that sheer inspection of the Brentano figure produces illusion decrement. However, illusion decrement was independent of the duration of the inspection period, with equivalent amounts of decrement occurring across the range of viewing times examined in the two experiments. The pattern of these results suggests that theories of Müller-Lyer decrement must incorporate a factor attributable to, or correlated with, inspection time, whose effect in reducing illusion magnitude is confined mainly to the first 1 or 2 min of active visual inspection of the Brentano illusion figure.

Effects of Training in Design on Magnitude of the Müller-Lyer Illusion

1976 ◽  
Vol 42 (1) ◽  
pp. 119-124 ◽  
Author(s):  
Jacques E. Letourneau
Keyword(s):  
Retinal Image ◽  
Size Constancy ◽  
Distant Object ◽  
Lyer Illusion ◽  
Design Students ◽  
Optometry Students

The Müller-Lyer illusion was measured for 10 design and 10 optometry students. The illusion was smaller for design students and they improved significantly with practice. The results are discussed in relation to size-constancy, according to which part of the figure corresponding to a distant object is overestimated and to the aptitude of design students to draw according to their retinal image.

Increases in scattered light causes increased darkness

2020 ◽  
Vol 2020 (15) ◽  
pp. 279-1-279-7
Author(s):  
John J. McCann
Keyword(s):  
Retinal Image ◽  
Dynamic Range ◽  
Scattered Light ◽  
Neural Mechanisms ◽  
The Other ◽  
Neural Processing ◽  
Spatial Transformation ◽  
Simple Consequence ◽  
Spatial Transformations ◽  
Spatial Redistribution

What we see is not a simple consequence of the light sent to our eyes. Vision has two powerful spatial transformations of scene luminances: one optical; the other neural. The first spatial redistribution of light is intraocular scatter. Scattered light reduces the dynamic range of the retinal image compared to light from the scene. The second spatial transformation comes from neural processing that causes appearances to vary with the scene’s content. A beach scene, (mostly max-luminance scene elements, and maximal scattered light) has the highest slope neural response function. The post-quanta-catch neural mechanisms overcompensate for the intraocular scatter. Low-reflectance objects look darker in scenes with maximal scatter

scholarly journals Most Findings Obtained With Untimed Visual Illusions Are Confounded

2021 ◽  
pp. 095679762199426
Author(s):  
Paola Bressan ◽  
Peter Kramer
Keyword(s):  
Time Course ◽  
Illusion Magnitude ◽  
Visual Illusions ◽  
Inspection Time ◽  
Local Processing ◽  
Ebbinghaus Illusion ◽  
Lightness Contrast ◽  
Or Groups ◽  
Presentation Time ◽  
Matching Adjustment

Visual illusions have been studied extensively, but their time course has not. Here we show, in a sample of more than 550 people, that unrestricted presentation times—as opposed to presentations lasting only a single second—weaken the Ebbinghaus illusion, strengthen lightness contrast with double increments, and do not alter lightness contrast with double decrements. When presentation time is unrestricted, these illusions are affected in the same way (decrease, increase, no change) by how long observers look at them. Our results imply that differences in illusion magnitude between individuals or groups are confounded with differences in inspection time, no matter whether stimuli are evaluated in matching, adjustment, or untimed comparison tasks. We offer an explanation for why these three illusions progress differently, and we spell out how our findings challenge theories of lightness, theories of global-local processing, and the interpretation of all research that has investigated visual illusions, or used them as tools, without considering inspection time.

Sign in / Sign up

Export Citation Format

Share Document