[psychophysical methods] An experimental paradigm which presents comparison stimuli in either increasing (ascending) or decreasing (descending) order until the subject indicates that the standard has been matched.
The concept was formalized by Gustav Fechner (1801-1887), a very interesting German who developed a strange malady in his late 30s and took to his bed to die, which he did—nearly 50 years later. Fechner also invented psychophysics as an answer to the mind-body problem. His book, Elements of Psychophysics, published in 1860, is seen by some historians of psychology as the beginning of psychology as an experimental science.