Wundt-Fick illusion

The illusion (inverted T), which is called the Wundt-Fick illusion at least in Japan, originates from A. Fick only, a physiologist who described it in his doctoral thesis in 1851- this is the first geometric-optical illusion. It was documented even before Oppel, in 1854 coined the term "geometrisch-optische Tauschung" and contributed several more patterns. Although he became a famous ophthalmologist, his son may be an even more famous ophthalmologist, as he invented the first contact lenses.

Fick, A. (1851) Da errone quodam optic asymmetria bulbi effecto. Marburg, Koch.

Tauschung: a is umlaut.

Neon color spreading

The neon color spreading effect proposed by van Tuijl is a special case observed in the Ehrenstein line-induced brightness illusion, descovered in 1941. Neon color spreading contains illusory contours, brightness induction, chromatic assimilation, and perceptual transparency (this gives depth perception). Neon color spreading can be also observed in the Kanizsa triangle (1955). In fact, Varin has first observed it in 1971, but the name "neon color" came from van Tuijl. A further outcome with the Ehrenstein lines - they can also cause lustre - was recently published by Pinna, Spillmann and Ehrenstein (2002).

In our (Jiro Gyoba, Kenzo Sakurai, Hideaki Kawabata and me) opinion, the neon effect shown in the Kanizsa triangle should be attributed to visual phantoms, especailly to photopic phantoms (Kitaoka et al., 1999). Actually, the photopic phantom illusion was first described in Rosenbach (1902) as its moving version.

Kitaoka, A., Gyoba, J., and Kawabata, H. (1999) Photopic visual phantom illusion: Its common and unique characteristics as a completion effect. Perception, 28, 825-834. MS-Word file (2.3MB)

Rosenbach, O. (1902) Zur Lehre von den Urtheilstauschungen. Zeitschrift fur Psychologie, 29, 434-448.

Thanks to Walter