Psychophysics

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.

Bibliography
The Fechner Weber