FREE ESSAY ON PSYCHOPHYSICS

PSYCHOPHYSICS

Psychophysics
The Weber -Fechner Principle: An Approximate psychological law relating the degree of
response or sensation of a sense organ and the intensity of the stimulus. The law asserts
that equal increments of sensation are associated with equal increments of the logarithm
of the stimulus, or that the just noticeable difference in any sensation results from a
change in the stimulus, which bears a constant ratio to the value of the stimulus.
Ernst Heinrich Weber (1795-1878)
Weber was the first German anatomist and physiologist to introduce the concept of the
just-noticeable difference, which is the smallest observable difference between two
similar stimuli. From 1818 until 1871 Weber was a professor at the University of Leipzig.
Weber is best known for his work on the sensory response to weight, temperature, and
pressure. Weber stated that, in order for any increase in the intensity of the stimulus a
threshold of sensation must be passed. This increase would create the just-noticeable
difference. The ratio Weber discovered was the total intensity of sensation, rather than
an absolute figure. Greater weight had to be added to heavier objects in order for the
person to notice the change. Weber's observations were formed mathematically by Gustav
Theodor Fechner, which he later called Weber's law.
Gustav Theodor Fechner (1801-1887)
Fechner was a German physicist and philosopher; he was an influential figure in the
development of psychophysics. He was concerned with the quantitative relations between
sensations and the stimuli producing them. When Fechner was 16, he began medical school
at the University of Leipzig where he studied anatomy under Weber. Fechner upon
graduation discovered his interested lead more toward physics and mathematics than
medicine.
Fechner by the end of the 1830's had written several papers on the perception of
complementary and subjective colors. In 1840 his article on subjective afterimages was
published. The same year he suffered a nervous collapse. Fechner had to quit his job at
the University due to his temporary blindness from staring at the sun during his
experiments. He returned in 1848 he completed when Nanna, which is a metaphysical
treatise that explains the philosophical treatment of relationship of mind to body. This
left a future program for psychophysics by linking increased bodily energy with an
increase in mental intensity.
From 1851 and 1860, Fechner worked on his psychophysical methods: just noticeable
differences, right and wrong cases and average error. He also did experiments on visual
distance and brightness. Fechner also lifted weights that lead to the first two volumes
of the Elemente der Psychophysik. The Elemente der Psychophysik was to distinguish an
exact science between physical and mental phenomena. The relationship between sensation
and nerve excitation was known as the inner psychophysics. The outer psychophysics was
referred to as the relationship between sensation and physical simulation. He developed
his famous principle: the intensity of a sensation increases as the log of the stimulus
(S = k log R) to characterize outer psychophysical relations. Fechner believed this was
demonstrating a fundamental philosophical truth: mind and matter are simply different of
conceiving of one and the same reality.
The philosophical message of the Elemente was widely ignored while; its orderly and
practical contributions were not. Fechner was a well trained, rational experimentalist
and a skillful mathematician and the influence of his work on scientists was accurate.
Terms of physical events could be linked to the measures of mental events. Fechner showed
the potential for quantitative, experimental exploration of the phenomenology of sensory
experience and established psychophysics as emerging scientific psychology. 
I decided to write my paper on psychophysics because I really do not know much about it.
The article I read was very interesting. Denis Leri the author of The Fechner Weber
Principle asked a few questions at the beginning of her article. In bright midday sun you
light a candle. Does anyone notice it getting brighter? I would have never thought the
candle would make the outside brighter. Will you identify my voice if I call you on a
cellular phone at a rock concert? I do not think I could pick out a familiar voice
because the noise level would be too loud. If you are carrying a refrigerator up a flight
of stairs and someone puts a hammer on it do you notice the difference? I would have said
the weight of the hammer would have made a difference. After reading this article I would
now say the ratio between the hammer and the refrigerator is greatly different and would
not cause a noticeable difference. I found psychophysics pretty interesting and I plan on
reading more about it.
Works Cited
? The Fechner Weber Principle @1997 Denis Leri
? Microsoft Bookshelf 98 Edition
I found my information by looking up psychophysics on the Internet and I found the
article by Denis Leri to be the most interesting. The italicized words are her exact
words are close to them.