Staring at the sun cost Gustav Fechner his eyes and gave psychology numbers
In 1839 a Leipzig physics professor damaged his eyes by gazing at the Sun through coloured glass to study afterimages. Forced to resign, Gustav Fechner turned to a question Kant had declared hopeless: can the mind be measured? His answer, a mathematical link between stimulus and sensation, helped turn psychology into an experimental science.
Fechner was born in 1801 at Gross Saerchen in Lower Lusatia, into a line of pastors. His free-thinking father, who had his children vaccinated and taught them Latin, died suddenly in 1806 and left the family destitute. After a brief spell studying medicine in Dresden, Fechner moved to Leipzig in 1818, took his doctorate there in 1823 and never left the city. Alongside chemistry and physics papers he wrote comic pieces, including a Comparative Anatomy of Angels published in 1825 under the pen name Dr. Mises.
Convalescing in bed after his eye injury, he glimpsed a quantitative bridge between physical and mental events. His Elements of Psychophysics of 1860 argued that body and consciousness are two faces of one reality and proposed that sensation grows with the logarithm of stimulus strength, written S = c log R. To make a feeling rise in equal steps, the stimulus has to multiply. The rule works well in the middle range but breaks down for very faint or very intense signals, and in 1961 S. S. Stevens published a paper titled To Honor Fechner and Repeal His Law, substituting a power law.
His curiosity roamed widely. He described colours appearing in spinning black-and-white patterns, now called the Fechner color effect, and a paradox in which a light looks brighter after one shaded eye is closed. He surveyed 73 synesthetes in 1871, is credited with introducing the median into data analysis, and guessed that cutting the corpus callosum would split one mind into two, an idea Roger Sperry and Michael Gazzaniga later found support for. His famous rectangle test seemed to favour the golden ratio, though he discarded inconvenient results and critics such as Mario Livio reject it.
Philosophically he was a panpsychist who saw the whole universe as alive, with humans placed between the souls of plants and those of stars. Gustav Mahler identified with him while composing, and Sigmund Freud cited him in The Interpretation of Dreams. Fechner died in 1887.
Source: Gustav Fechner
