- positive afterimage
- A term used to denote an afterimage that has the same relative brightness relations as the primary optical stimulus (for example, a dark blue afterimage of a dark blue pen). The term positive afterimage is used in opposition to the term * negative afterimage, which refers to an afterimage that manifests itself in complementary colours (for example, a dark blue afterimage of a bright yellow pen). Two physiologically occurring positive afterimages are *Hering's afterimage and the * Hess afterimage. The occurrence of pathological positive afterimages has been reported in drug-induced states such as LSD and mescaline intoxication, as well as in drug-induced * flashback phenomena and *hallucinogen-induced persistent perception disorder (HPPD). Phenomenologically as well as conceptually, these latter types of positive afterimage would seem to be closer akin to central phenomena such as *palinopsia, *polyopia, and the * trailing phenomenon, than to physiological afterimages, which are generally considered to be * entoptic in origin. The positive afterimage may be classified as a * physiological illusion.ReferencesAbraham, H.D. (1983). Visual phenomenology of the LSD flashback. Archives of General Psychiatry, 40, 884-889.Brown, J.L. (1965). Afterimages.In: Vision and visual perception. Edited by Graham, C.H. New York, NY: Wiley.
Dictionary of Hallucinations. J.D. Blom. 2010.