Joseph Delboeuf

Joseph Rémi Léopold Delbœuf (30 September 1831, Liège, Belgium – 14 August 1896, Bonn, Germany) was a Belgian experimental psychologist who studied visual illusions including his work on the Delboeuf illusion. He studied and taught philosophy, mathematics, and psychophysics. He published works across a diverse range of subjects including the curative effects of hypnotism. Joseph Delboeuf was born in the French speaking town of Liège, Belgium. His father, a pewter craftsman, died early in Delboeuf’s life. He studied at the University of Liège, earning his PhD in philosophy in 1855, followed by physics and mathematics in 1858. He received a scholarship from the University of Bonn and continued his postdoctoral research under philosopher and mathematician Friedrich Ueberweg. In 1860, he began teaching Greek at l’Ecole Normale des Humanités de Liège. In 1863, he was given the post of Maitre de Conférences, which he only held for a few months before being appointed Chair of Philosophy at University of Ghent, leaving his research in mathematics. There, he met Joseph Plateau, who helped him publish his first two notes on optical illusions in the Bulletin of the Royal Academy of Belgium. He then began his research in psychophysics with Gustav Fechner in 1865. Delboeuf began his psychophysical experimentation on brightness in 1865 with Gustav Fechner. Delboeuf introduced the concept of sense distance (contraste sensible). Delboeuf is known for his description of the Delboeuf illusion in 1893. Many experiments have been performed on this illusion since that time. After completing work on sleep and dreams, Delboeuf started researching magnetism and hypnotism. At the First International Congress on scientific and experimental hypnotism (1889), a motion was put forward to ban non-medical practitioners from using hypnosis. However, Delboeuf argued that a medical degree was not required to practice hypnotism; rather, it should be used freely, yet with caution.