The hermann grid illusion revisited

An inverse scintillating grid, that also produces the scintillating effect Media Licence: Public Domain The scintillating grid is a simultaneous lightness contrast illusion of a similar type to the Hermann gridalthough it was discovered over a century later by J. Bergen as reported in Schrauf et al. One important difference is that the scintillating grid figure comprises white dots at the intersection of grey gridlines on a black ground, whereas there are no such dots on the Hermann grid, and so any dots which might appear within the Hermann grid are purely artefacts of the visual system.

The hermann grid illusion revisited

The grey blobs disappear when looking directly at an intersection. Scintillating grid illusion[ edit ] An example of the scintillating grid illusion.

Dark dots seem to appear and disappear at intersections The scintillating grid illusion is an optical illusiondiscovered by E. Lingelbach inthat is usually considered a variation of the Hermann grid illusion. It is constructed by superimposing white discs on the intersections of orthogonal gray bars on a black background.

Dark dots seem to appear and disappear rapidly at random intersections, hence the label "scintillating". When a person keeps his or her eyes directly on a single intersection, the dark dot does not appear. The dark dots disappear if one is too close to or too far from the image. Differences between the scintillating and Hermann grid illusions[ edit ] The difference between the Hermann grid illusion and the scintillating illusion is that scintillating illusions have dots already in place at the intersection, whereas there are no dots already in place at the intersections of Hermann grid illusions.

Since they are so similar, the two names are commonly used interchangeably. This requirement suggests the participation of global processes of the kind proposed for the linking and grouping of features in an image, in addition to local processes. In the center of the receptive field the individual photoreceptors excite the ganglion cell when they detect increased luminance.

The photoreceptors in the surrounding area inhibit the ganglion cell. Thus, since a point at an intersection is surrounded by more intensity than a point at the middle of a line, the intersection appears darker due to the increased inhibition.

There is strong evidence that the retinal ganglion cell theory is untenable. For example, making the lines of the grid wavy rather than straight eliminates both the Hermann grid and scintillating grid illusions.

Hermann Grids, An optical Illusion Best Avoided – Blog

Lateral inhibition theory also can not account for the fact that the Hermann grid illusion is perceived over a range of bar widths.

One alternative explanation is that the illusion is due to S1 type simple cells in the visual cortex.The Hermann grid illusion consists of smudges perceived at the intersections of a white grid presented on a black background. In the effect was first explained by a theory advanced by Baumgartner suggesting the illusory effect is due to differences in the discharge characteristics of retinal ganglion cells when their receptive fields fall along the intersections versus when they fall.

Hermann Grid Illusion Revisited." Perception 34 (11): – Color of smudges is defined by which set of lines is in front. On left color lines are in front and smudges have the same color.

On right Vision Lecture 9 Notes: Illusions Author: Schiller, Peter H Created Date. The Hermann grid illusion revisited. Perception-London, 34(11), Spillmann L, Zur Feldorganisation der visuellen Wahrnehmung beim Menschen.

The hermann grid illusion revisited

Vergleichende. psychophysische Untersuchung der GrojJe rezeptiver Felder im zentralen und peripheren Gesichtsfeld. The Hermann grid illusion consists of smudges perceived at the intersections of a white grid presented on a black background. In the effect was first explained by a theory advanced by.

The Hermann grid illusion is an optical illusion characterized by "ghostlike" grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection.

The scintillating grid is a simultaneous lightness contrast illusion of a similar type to the Hermann grid, although it was discovered over a century later by J. R. Bergen () (as reported in Schrauf et al. ()). One important difference is that the scintillating grid figure comprises white dots at the intersection of grey gridlines on a.

Grid Illusions: Hermann Grid