Mechanisms and functions of visual illusions

Joint Workshop on Machine Perception and Robotics
Invited Talk II: 13:10-14:10, November 1, 2013
Suzaku campus, Ritsumeikan University, Kyoto, Japan

KITAOKA Akiyoshi (北岡明佳) (Ritsumeikan University, Deptment of Psychology) email HP

since October 27, 2013 　Abstract

Visual illusion refers to a phenomenon that the perception of an object or its properties is different from what it should ‘objectively’ be. There are a variety of visual illusions including the geometrical illusion (shape illusion), color illusion, lightness illusion, motion illusion, impossible figures, reversible figures, trompe l'oeil, etc., depending on visual attributes or characteristics. Mechanisms and functions are fairly understood for some illusions while not for others.

Ames room and the Hering illusion

Thans to Dr. Stevanov and Dr. Wakabayashi

In Japan, the ‘functional’ illusion is distinguished from the ‘not-functional’ illusion. To put it simply, the former is called "damashie" (騙し絵, trompe l'oeil) in Japanese, while the latter is called "sakushi" (錯視, visual illusion in a narrow sense) in Japanese. For example, the Ames room, a kind of trompe l'oeil, can be understood in terms of competition between shape constancy (形の恒常性) and size constancy (大きさの恒常性). Both are functional. On the other hand, the ‘Rotating snakes’ illusion created by Kitaoka in 2003 shows illusory motion in a static image but has not been accounted for in terms of any function. Actually sakushi is translated to visual illusion or optical illusion, but they are not equal.

Trapezoids appear to be rectangles which tilt in depth (= shape constancy: 形の恒常性).

Rectangles appear to be rectangles which are placed in a frontoparallel plane (= shape constancy).

Left: Ambiguous image. Upper-right: The two persons appear to be 'actually the same size' though the retinal sizes are different (= size constancy). Lower-right: The left person appears to be much smaller than the right one (= Ames room situation), probably because the rectangle in their back gives information that the two persons stand at nearly the same distances. That is, the effect of shape constancy overcomes that of size constancy in this situation.

This (Ames room) is kind of visual illusion, but is not necessarily kind of sakushi (錯視) in Japanese because sakushi refers to be 'not-functional' illusions such as motion illusion in a static images as shown below. I would like to learn how they are categorized in China, Korea, as well as other Asian countries.

"Rotating snakes"
(a remke)

Yet, there are some illusions which are ambiguous and cannot be perfectly classified into either of the two categories.

"Ritsumeikan flags"

In the left image, there are no red components but the flag appears to be reddish to some degree.

Demo print DOC

References

北岡明佳　（2011）　色の錯視いろいろ　（2）色の恒常性と2つの色フィルタ　日本色彩学会誌, 35(3), 234-236. PDF, PDF (high-resolution）

北岡明佳　（2011）　色の錯視いろいろ　（1）「目の色の恒常性」という錯視の絵　日本色彩学会誌, 35(2), 118-119. PDF

Q: Which of the three colors shown below is the same color as the moon?

Additive color changes

北岡明佳　（2011）　色の錯視いろいろ　（2）色の恒常性と2つの色フィルタ　日本色彩学会誌, 35(3), 234-236. <図2>

Multiplicative color change

北岡明佳　（2011）　色の錯視いろいろ　（2）色の恒常性と2つの色フィルタ　日本色彩学会誌, 35(3), 234-236. <図4>

A Color Contrast-Color Constancy Continuum

The color contrast effect is continual with the additive type of color constancy. The more articulated the image is, the stronger the color contrast effect, which leads to color constancy.

Spiral illusion

The spiral illusion is kind of tilt illusion shown in concentric circles.

Fraser's spiral

The term "spiral illusion" had long referred to the spiral illusion of the Fraser illusion (Fraser, 1908) before we elucidated that any tilt illusion can form spiral illusion (Kitaoka, Pinna and Brelstaff, 2001). This page shows a copy of Fraser's spiral produced by PC programming. <2003/8/30>

Fraser, J. (1908) A new visual illusion of direction. British Journal of Psychology, 2, 307-320.

Kitaoka, A., Pinna, B., and Brelstaff, G. (2001). New variations of spiral illusions. Perception, 30, 637-646.

Catalogue of spiral illusions

北岡明佳（2006）渦巻き錯視のメカニズム　じっきょう数学資料, 52, 13-15. PDF

Tilt illusion is a subcategory of geometrical illusion, in which lines or edges appear to tilt clockwise or counterclockwise. (e.g., Zöllner illusion, Fraser illusion, Café Wall illusion)

Spiral illusion can be formed with any tilt illusion.

Spiral illusion of the Fraser illusion

"Spiral blood vessel"

Red concentric rings appear to be a spiral that approaches the center rotating clockwise.

Simple version of the spiral illusion of the Fraser illusion

Concentric rings of black and white line segments appear to be spirals that approach the center rotating counterclockwise.

Spiral illusion of the Café Wall illusion

Spiral illusion of the Cafe Wall illusion

"Rotating spiral illusions"

Concentric circles appear to be spirals.

Spiral illusion of the Zöllner illusion

"Spiral warp"

Concentric rings appear to be spirals.

equiangle = 45 deg

Spiral illusion of the Zöllner illusion

The spiral illusion of the Zöllner illusion:

Kitaoka, A., Pinna, B., and Brelstaff, G. (2001). New variations of spiral illusions. Perception, 30, 637-646.

Spiral illusion of the Popple illusion

Spiral illusion of the illusion of fringed edges

Spiral illusion of the illusion of Y-junctions

"Neural circuit spirals 2"

Concentric circles appear to be spirals (going to the center by rotating clockwise). Moreover, the inner part appears to rotate clockwise (counterclockwise) when observers approach (move away from) the image keeping their eyes fixed at the center.

Spiral illusion of the fractal tilt illusion

"Fractal spiral illusion"

Concentric rings made up of fractal islands appear to form spirals.

Copyright Hitoshi & Shinobu Arai 2007
from Professor Hitoshi Arai, Graduate School of Mathematical Sciences, University of Tokyo, October 4, 2007

The first illusion image made up of fractals!

視覚数学e研究室報告

Suggested function
Kitaoka, A., Pinna, B., and Brelstaff, G. (2001). New variations of spiral illusions. Perception, 30, 637-646.

Bernoulli's spiral

r = a exp (k θ)

= equiangular spiral

k = 1 / tan (φ)

Concentric (φ = 90º), radial (φ = 0º), and spiral (0º < φ < 90º)

Kitaoka, A., Pinna, B., and Brelstaff, G. (2001). New variations of spiral illusions. Perception, 30, 637-646.

Model:

1. Orientation-selective neurons in V1 detect the orientation of the line or edge in each local area.

2. Polar-coordinates neurons in V4 collect information from the V1 cells and judge φ.

3. If φ = 90º, the pattern is regarded as Concentric. If φ = 0º, the pattern is regarded as Radial. If 0º < φ < 90º, the pattern is regarded as Spiral.

4. In spiral illusion images, V1 cells should output φ = 90º but send false information of orientation (0º < φ < 90º ) due to tilt illusion.

5. Then, V4 neurons misjudge it and report "it is a spiral pattern"!

幾何学的錯視の一覧（Geometrical illusions）

Anomalous motion illusion refers to motion illusion in a stationary image, in which part of the stationary image appears to move. (e.g., Ouchi illusion, Enigma illusion, optimized Fraser-Wilcox illusion)

Visual delay-dependent motion illusion

1. High-luminance parts show shorter latency than low-luminance part.

2. High-contrast parts show shorter latency than low-contrast part. <our finding!>

Kitaoka, A. and Ashida, H. (2007) A variant of the anomalous motion illusion based upon contrast and visual latency. Perception, 36, 1019-1035. PDF

cf. fluttering-heart illusion

(Helmholtz, 1867; Nguyen-Tri and Faubert 2003; von Grünau 1975a, 1975b, 1976; von Kries 1896)

References

Helmholtz, H. von (1856, 1860, 1866, 1867) Handbuch der Physiologischen Optik. Leipzig: Voss. Part I (1856), Part II (1860), Part III (1866). The first two parts were published in the same volume as the third part in 1866. This was called the first edition according to Robinson (1972). In many case, “1867” is preferred for citation as follows. Helmholtz, H. von. (1867). Handbuch der physiologischen Optik. Leipzig: Voss. Translated by J P C Southall of the third German edition (1909-1911) was published as Treatise on Physiological Optics, New York: Dover (1924-1925, 1962). Edited by N. Wade, Helmholtz's Treatise on Physiological Optics, Bristol: Thoemmes (2000). The following information was taken from Wade (2004).

Helmholtz H, 1867 "Handbuch der physiologischen Optik", in Allgemeine Encyklopädie der Physik volume 9, Ed. G Karsten (Leipzig: Voss)
Helmholtz H, 1896 Handbuch der physiologischen Optik 2nd edition (Hamburg: Voss)
Helmholtz H, 1909 Handbuch der physiologischen Optik volume 1, 3rd edition, Eds A Gullstrand, J von Kries, W Nagel (Hamburg: Voss)
Helmholtz H, 1910 Handbuch der physiologischen Optik volume 3, 3rd edition, Eds A Gullstrand, J von Kries, W Nagel (Hamburg: Voss)
Helmholtz H, 1911 Handbuch der physiologischen Optik volume 2, 3rd edition, Eds A Gullstrand, J von Kries, W Nagel (Hamburg: Voss)
Helmholtz H, 1924 Helmholtz's Treatise on Physiological Optics volume 1, translated by J P C Southall (New York: Optical Society of America)
Helmholtz H, 1925 Helmholtz's Treatise on Physiological Optics volume 2, translated by J P C Southall (New York: Optical Society of America)
Helmholtz H, 1925 Helmholtz's Treatise on Physiological Optics volume 3, translated by J P C Southall (New York: Optical Society of America)
Helmholtz H, 2000 Helmholtz's Treatise on Physiological Optics (3 volumes) translated by J P C Southall (Bristol: Thoemmes)

"Fluttering red hearts in front of the blue background 3"

Hearts appear to move when the image is moved or your pair of glasses are moved. This illusion is enhanced in a dark condition or in the mesopic vision.

"Fluttering red hearts in front of the blue background"

Hearts appear to move when the image is moved or your pair of glasses are moved. This illusion is enhanced in a dark condition or in the mesopic vision.

"Fluttering red hearts in front of the green background"

Hearts appear to move when the image is moved or your pair of glasses are moved. This illusion is enhanced in a dark condition or in the mesopic vision.

"Fluttering red hearts in front of the red-purple background"

Hearts appear to move when the image is moved or your pair of glasses are moved. This illusion is enhanced in a dark condition or in the mesopic vision.

"Fluttering green hearts in front of the red background"

Hearts appear to move when the image is moved or your pair of glasses are moved. This illusion is enhanced in a dark condition or in the mesopic vision.

Fraser-Wilcox illusion group

「蛇の回転」

"Rotating snakes"

"Rotating red disks"

Each disk appears to rotate clockwise when this image is presented on a bright PC display or on a print with a bright environment.

Each disk appears to rotate conterclockwise when this image is presented on a dark PC display or on a print with a dark environment.

Conclusion in advance

"Moving snakes with a cloud of dust"

Snakes appear to move horizontally.

"Moving arrows illusion"

Arrows appear to move.

"Blooming flowers"

Flowers appear to expand.

「ぐいぐい昇竜」
Ascending dragon

竜が昇っていくように見える（下から見たところ）。
An dragon appears to rise.

"Dongurakokko" (The donguri wave)

Donguri (acorns) appear to wave.

「トロの波」

図が波打って見える。

A brief history of phenomenal aspects of the Fraser-Wilcox illusion group

<Kitaoka, A. (forthcoming). The Fraser-Wilcox illusion and its extension. In Shapiro, A. and Todorovic, D. (Eds.), Oxford Compendium of Visual Illusions. Oxford University Press.>

1. Fraser and Wilcox (1979)

References

Fraser, A. and Wilcox, K. J. (1979). Perception of illusory movement. Nature, 281, 565-566.

Observers saw illusory motion in a stationary image which consists of repeated luminnace gradient in a saw-tooth wave form. Some reported illusory motion from dark to light along a luminance gradient, while others saw the reversal. The illusion is strong in the peripheral viewing. Fraser and Wilcox (1979) claimed that this individual difference depends on some genetic properties.

Adopted from “Alex Fraser, Geneticist and Painter”
(http://doctoralexfraser.blogspot.jp/p/spirals.html) <access August 25, 2012> (with permission from Alan Fraser)

Alex Fraser (1923-2002) was a geneticist and a painter.

2. Faubert and Herbert (1999)

The left disk appears to rotate clockwise while the right one counterclockwise. Faubert and Herbert (1999) reported only illusory motion from dark to light along a luminance gradient. They attributed the illusory motion to the assumed time difference between responses to black and white.

References

Faubert, J. and Herbert, A. M. (1999). The peripheral drift illusion: A motion illusion in the visual periphery. Perception, 28, 617-621.

3. Naor-Raz and Sekuler (2000)

The left disk appears to rotate clockwise while the right one counterclockwise. Naor-Raz and Sekuler (2000), too, reported only illusory motion from dark to light along a luminance gradient. They revealed that the illusion magnitude is a positive, nearly linear function of contrast.

References

Naor-Raz, G. and Sekuler, R. (2000). Perceptual dimorphism in visual motion from stationary patterns. Perception, 29, 325-335.

This disk appears to rotate clockwise.

This color illusion image presented by Naor-Raz and Sekuler (2000) (shown below) might be attributable to this type.
http://www.perceptionweb.com/perception/perc0300/sekuler.jpg <access August 26, 2012>
<with permission from Robert Sekuler>

4. Kitaoka and Ashida (2003)

The left disk appears to rotate counterclockwise while the right one clockwise. Kitaoka and Ashida (2003) proposed that the illusory motion is strong when patterns are arranged in the following luminance order: from black, dark-gray, white, light-gray, and back to black.

References

Kitaoka, A. and Ashida, H. (2003). Phenomenal characteristics of the peripheral drift illusion. VISION (Journal of the Vision Society of Japan), 15, 261-262. PDF

5. Kitaoka (2007)

high-resolution file

Kitaoka (2007) classified the Fraser-Wilcox illusion into Type I, IIa, IIb and III, in each of which the dark-to-light type was distinguished from the light-to-dark one.

References

Kitaoka, A. (2007) Phenomenal classification of the “optimized” Fraser-Wilcox illusion and the effect of color. Poster presentation in DemoNight, VSS2007, GWiz, Sarasota, Florida, USA, May 14, 2007.

Type I

"Dark to light"
The left disk appears to rotate counterclockwise while the right one clockwise.

"Light to dark"
The left disk appears to rotate counterclockwise while the right one clockwise.

"Dark to light" and "light to dark" combined
The left disk appears to rotate counterclockwise while the right one clockwise.

"Dark to light" and "light to dark" combined, with color enhancement
The left disk appears to rotate counterclockwise while the right one clockwise.

The upper-left, upper-right, and lower-middle disks appear to rotate counterclockwise while the rest clockwise.

Type I (six disks) 1500 x 1000 (pixel)

Type I (six disks) 6000 x 4000 (pixel)

Type II

Type IIa

The upper-left, upper-right, and lower-middle disks appear to rotate counterclockwise while the rest clockwise.

Type IIb

The upper-left, upper-right, and lower-middle disks appear to rotate counterclockwise while the rest clockwise.

Type IIa (six disks) 1500 x 1007 (pixel)

Type IIa (six disks) 6000 x 4031 (pixel)

Type IIb (six disks) 1500 x 1000 (pixel)

Type IIb (six disks) 6000 x 4000 (pixel)

"Rotating snakes"
(Ver. 2011)

Each disk appears to rotate.

Adjusted for printing using EPSON PM-4000PX

Type III

The upper row appears to move rightward while the lower one leftward.

Type III (two rows) 1500 x 400 (pixel)

Type III (two rows) 4500 x 1200 (pixel)Type III 4500 x 1200

The upper-left, upper-right, and lower-middle disks appear to rotate counterclockwise while the rest clockwise.

6. Kitaoka (2008a, b)

"Type IV" was added to the list.

References

Kitaoka, A. (2008a). Optimized Fraser-Wilcox illusions: a pictorial classification by Akiyoshi Kitaoka. Talk in Workshop No.005 "Experimental studies of anomalous motion illusions" in the 72nd Annual Convention of the Japanese Psychological Association, Hokkaido University, Sapporo, Japan, September 19, 2008. Talk

Kitaoka, A. (2008b). A new type of the optimized Fraser-Wilcox illusion in a 3D-like 2D image with highlight or shade. Journal of Three Dimensional Images (Japan), 22(4), 31-32. PDF PDF (manuscript) Presentation

Type IV

The upper-left, upper-right, and lower-middle rings appear to rotate counterclockwise while the rest clockwise.

Type	dark to light	light to dark	Examples
IV new!

Findings of the "Rotating snakes" illusion (optimized Fraser-Wilcox illusion)

1. Illusion is strong in the peripheral vision

Kitaoka, A. and Ashida, H. (2003) Phenomenal characteristics of the peripheral drift illusion. VISION, 15, 261-262.PDF

2. Illusion is strong when the image is of high luminance

Hisakata, R. and Murakami, I. (2008) The effects of eccentricity and retinal illuminance on the illusory motion seen in a stationary luminance gradient. Vision Research, 49, 1940-1948.

3. Illusion requires some eye movement

Murakami, I., Kitaoka, A. and Ashida, H. (2006) A positive correlation between fixation instability and the strength of illusory motion in a static display. Vision Research, 46, 2421-2431.

Kuriki, I., Ashida, H., Murakami, I., and Kitaoka, A. (2008) Functional brain imaging of the Rotating Snakes illusion by fMRI. Journal of Vision, 8(10):16, 1-10.

4. Illusion does not occur in the stabilized retinal image

Murakami, I., Kitaoka, A. and Ashida, H. (2006) A positive correlation between fixation instability and the strength of illusory motion in a static display. Vision Research, 46, 2421-2431.

5. Illusion is enhanced by color

Kitaoka, A. (2007) Phenomenal classification of the “optimized” Fraser-Wilcox illusion and the effect of color. Poster presentation in DemoNight, VSS2007, GWiz, Sarasota, Florida, USA, May 14, 2007.

6. Illusion is weak when the image is moved

Tomimatsu, E., Ito, H., Seno, T., and Sunaga, S. (2010) The ‘rotating snakes’ in smooth motion do not appear to rotate. Perception, 39, 721-724.

7. Illusion is weak when the image is observed through pinholes

Cantor, C. R. L., Tahir, H. J., and Shor, C. M. (2010) Is the rotating snakes an optical illusion? VSS2010, #26.434.

8. Illusion activates V1 through hMT+ areas

Kuriki, I., Ashida, H., Murakami, I., and Kitaoka, A. (2008) Functional brain imaging of the Rotating Snakes illusion by fMRI. Journal of Vision, 8(10):16, 1-10.

Ashida, H., Kuriki, I., Murakami, I., Hisakata, R. and Kitaoka, A. (2012). Direction-specific fMRI adaptation reveals the visual cortical network underlying the "Rotating Snakes" illusion. NeuroImage, 61, 1143–1152.

Major models of the "Rotating snakes" illusion (optimized Fraser-Wilcox illusion)

1. Adaptation (temporal positional shift)

Backus, B. T. and Oruç, I. (2005) Illusory motion from change over time in the response to contrast and luminance. Journal of Vision, 5, 1055-1069.

2. Visual delay (temporal positional shift) related issue 1 _ related issue 2

Conway, R. B., Kitaoka, A., Yazdanbakhsh, A., Pack, C. C., and Livingstone, M. S. (2005) Neural basis for a powerful static motion illusion. Journal of Neuroscience, 25, 5651-5656.

3. Motion signal asymmetry

Murakami, I., Kitaoka, A. and Ashida, H. (2006) A positive correlation between fixation instability and the strength of illusory motion in a static display. Vision Research, 46, 2421-2431.

7. Kitaoka (2008, 2010, 2012a, b)

A strongly color-dependent, "reddish" version was added to the list.

In 2008, Kitaoka found that the direction of illusory motion is “red → dark purple → purple → magenta (light red-purple) → red”, and that the illusion magnitude is strong when overall luminance contrast is low. Images of high luminance make a strong effect.

"Rotating red fruits"

Rings of fruits appear to rotate.

Purple » light purple » light red-purple » red » purple

References

Kitaoka, A. (2010). Introduction to visual illusion. Tokyo: Asakura-shoten (in Japanese). Book

Kitaoka, A. (2012a). Designs using the red Fraser-Wilcox illusion. Journal of the Color Science Association of Japan, 36, Supplement, 188-189. PDF (color manuscript) Talk

Kitaoka, A. (2012b) The Fraser-Wilcox illusion and its extension. Perception 41 ECVP Abstract Supplement, page 91 (Poster September 3, 2012). Poster PDF

8. Kitaoka (2011)

In 2011, Kitaoka found that flickering the image increases the illusion magnitude. Blinks also work.

Further studies on the flickering enhancement or induction (Kitaoka, 2013)

Flickering induction depends on the interaction between the stimulus and the blank.

Each disk appears to rotate clockwise during fading-in while counterclockwise during fading-out.

Each disk appears to rotate counteclockwise during fading-in while clockwise during fading-out.

Each disk appears to expand during fading-in while to contract during fading-out.

"On-off rotating snakes: red and sky blue #1"

When fading in, each disk appears to rotate in the direction: black, red, white, sky blue, black. The direction is reversed when fading out.

"On-off rotating snakes: red and sky blue #2"

When fading in, each disk appears to rotate in the direction: black, sky blue, white, red, black. The direction is reversed when fading out.

9. Yanaka and Hirano (2011)

Yanaka and Hilano (2011) reported that this illusion is enhanced by mechanical shaking.

Each disk appears to rotate counterclockwise.
(Note that this movie is not their original)

References

Yanaka, K. and Hilano, T. (2011). Mechanical shaking system to enhance "Optimized Fraser–Wilcox Illusion Type V". Perception, 40, ECVP Abstract Supplement, page 171.

10. Yanaka (2012)

Yanaka (2012) reported that this illusion is enhanced by viewing images under dark illumination.

References

Yanaka, K. (2012). Enhancement of the optimized Fraser-Wilcox illusion Type V by swinging the image. Talk in the 5th Illusion Workshop, Meiji University, Tokyo, Japan, September 18, 2012.

11. Kitaoka (2013)

In 2013, Kitaoka (ECVP2013) found that Yanaka’s darkening enhancement is accompanied by a reversal of illusion: i.e., the direction under dark condition is “red → magenta (light red-purple) → purple → dark purple → red”.

References

Kitaoka, A. (2013). Invisible color and visible color: Mystery of color the brain feels. Talk in the Shizuoka Science Museum Ru-Ku-Ru, Shizuoka, Japan, January 13, 2013. Talk

12. Kitaoka (2013)

In 2013, Kitaoka (ECVP2013) found that combination of a long wavelength color and a short one makes the illusions.

Illusory motion depending on the combination of colors