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. 2019 Nov 28;10(6):2041669519892012.
doi: 10.1177/2041669519892012. eCollection 2019 Nov-Dec.

The Sequin Illusion

Yi-Tsen Kuo  1 , Philip Tseng  1
Affiliations

The Sequin Illusion

Yi-Tsen Kuo et al. Iperception. .

Abstract

The Sequin Illusion can be seen when shapes are drawn in dotted lines, against a background of different brightness. This can be done either with bright dots over a dark background or with dark dots over a bright background, though the latter usually works better. The illusion appears as a wave of dark (or bright) spots inside the dotted shapes (like sequins!) in peripheral vision. Although similar in appearance with the Hermann Grid, the Sequin Illusion occurs inside the shapes; persists despite slanted, disrupted, or nonrectangular edges; and is only eliminated when the dotted contour is formed by colors of similar brightness. Therefore, this illusion is driven by brightness (not color) contrasts in contours, which possibly points to the magnocellular channel in lateral geniculate nucleus.

Keywords: Hermann Grid; brightness contrast; luminance contrast; perception; perceptual fill-in.

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Figures

Figure 1.
Figure 1.
The Sequin Illusion (top) consists of fleeting shadowy spots in the periphery, which is similar to the Hermann Grid (bottom, left). There are many ways to weaken the Hermann Grid, such as discontinuous or offset lines and edges (bottom, middle, and right; adapted from Schiller & Carvey, 2005), though the illusion still persists to some degree.
Figure 2.
Figure 2.
Unlike the Hermann Grid, the Sequin Illusion is less sensitive to (a) offset lines, (b) slanted lines, and (c) nonrectangular shapes.
Figure 3.
Figure 3.
The illusion works with bright lines over darker background (top) as well as darker lines over brighter background (bottom), though the latter seems to make the shadowy spots easier to observe and thus is the choice of demonstration in this report.
Figure 4.
Figure 4.
With equiluminant borders, the illusion is eliminated and becomes a Hermann Grid. Thus, we confirm that it is the brightness contrast that makes dotted lines special.
Figure 5.
Figure 5.
The illusion appears when bright/dark alternating contrast is in the contour. The second color does not have to be the same color as the background as it is the brightness contrast that is driving the illusion here. Multiple colors can also be used as long as their brightness alternate.
See this image and copyright information in PMC

References

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How to cite this article

    1. Kuo Y.-T., Tseng P. (2019). The Sequin Illusion. i-Perception, 10(6), 1–7. doi:10.1177/2041669519892012 - PMC - PubMed

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