Psychophysics Essays - Psychology, Cognitive Science, Neuroscience

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