Joseph Delboeuf

Joseph Rémi Léopold Delbœuf (September 30, 1831 in Liege, Belgium – August 14, 1896 in Bonn, Germany) was a Belgian philosopher, mathematician, experimental psychologist, hypnotist and psychophysicist. He was a highly respected as a psychologist in his lifetime, the author of an extensive and diverse works, and is known for his work on hypnosis as well as for his important contribution to the debate around the psychophysical.

In 1860 he became an instructor in the normal school of Liege, and in 1863-66 was professor of philosophy in Ghent. Beginning in 1866, he was professor at University of Liège.

Delboeuf began his psychophysical experimentation on brightness in 1865 with Gustav Fechner. The most important idea that Delboeuf introduced to psychophysics was that of the sense distance (contraste sensible).

Delboeuf is probably best known for his description the Delboeuf illusion in 1893. Many experiments have been performed on this illusion since that time.

...
Wikipedia