| Chubb Illusion - The Concept | | | | To perform the original experiment, Chubb and his |
| In the year 1989, the Professor of Cognitive | | | | team used an intricate black and white pattern, as |
| Sciences at the University of California, Charlie | | | | the contextual texture and a central design. In the |
| Chubb and his colleagues discovered a visual | | | | central design, white color was replaced by a |
| phenomenon, where the contrast of an object | | | | shade of gray. Against the black and white |
| appears dramatically different when viewed in | | | | backdrop, the central figure appeared less bright |
| varying contexts. This anomaly came to be | | | | than it did when viewed alone. In the second |
| known as Chubb Illusion. According to the theory, | | | | phase, the same central pattern was seen against |
| a low-contrast design appears higher in contrast | | | | a gray background with lesser brightness than the |
| when surrounded by a uniform color field. | | | | gray color of the central design. Here, the figure in |
| However, when the same design is viewed | | | | the middle appeared brighter than actual. |
| against a high-contrast field, it appears | | | | The Details |
| comparatively lower in contrast. | | | | Chubb Illusion is more distinctly visible in a |
| The Experiment | | | | 'perfectly transmitting medium,' where there is no |
| To demonstrate the variation of an illuminant | | | | obstruction due to glass surface, liquids, fog, |
| stimulus, as a function of its context, the target | | | | smog, or other suspended particles. Further, the |
| pattern was embedded in a texture with same | | | | objects should not be placed at a long distance |
| 'spatial frequency,' but different brightness. Spatial | | | | from the viewer. In an imperfectly transmitting |
| frequency of a structure is the frequency with | | | | medium, the difference between the perceived |
| which it repeats per unit distance. In visual | | | | contrasts is not as marked as in the case of a |
| perception parlance, spatial frequency is measured | | | | perfectly transmitting medium. The visual cognition |
| in the terms of repetitions, with reference to the | | | | is a result of reflection. Our eyes capture the light, |
| visual angle (the angle of view). To study the | | | | the objects reflect, which helps us to view them. |
| capabilities of human visual systems, 'sinusoidal | | | | The imperfectly transmitting medium obstructs or |
| gratings' are employed. Sinusoidal gratings are | | | | otherwise influences the transmitted light being |
| images with the bands of black and white colors, | | | | captured by the eyes. This diminishes the effects |
| spread across a field. | | | | of Chubb Illusion. |