Early Studies of the Central Nervous System

Stephen Hales (1677–1761) English Botanist Worked with frogs. Hales showed that some reflexes are mediated by the spinal cord. Hales studied stones taken from the bladder and kidneys and suggested solvents which might reduce them without surgery. He also invented the surgical forceps.                        

Okay, it is the History Channel but . . . . .

Luigi Galvani~ 1780 Luigi Galvani touched the nerves of a frog's spinal cord with metal electrodes which caused contractions of the leg muscles. Galvanic Skin Response named after him, but not invented by him.

Charles Bell - 1823 Scottish surgeon-anatomist published "Essays on the Anatomy of Expression in Painting" Nerves of the senses could be traced from specific areas of the brain to their end organs. Distinguished between sensory & Motor neurons

Germany – birthplace of Psychology 1815 – 1871 – federation of 38 principalities. Wissenschaft – philosophy of education encouraged research, teaching academic freedom students wandered from university to university degrees involved sitting examinations or writing of thesis. Methods from Physiology Development of measurement instruments Replication of results Public data and academic debate Experimental methods

Johannes Peter Müller 1840 – further developed Bell’s research . The doctrine of Specific Nerve Energies Nervous stimulation is the link between the physical world and our psychological experience of it. For example, the visual nerves, however they may be stimulated, are only capable of transmitting visual data.

The immediate objects of the perception of our senses are merely particular states induced in the nerves and felt as sensations either by the nerves themselves or the parts of the brain concerned with sensations. The nerves make known to the brain, by virtue of the changes produced in them by external causes, the changes of condition of external bodies.

Mechanistic View of Human Behavior Müller – proposed that there was in addition to physical and chemical properties of the physiological system, there was also a “Vital Force” that could not be reduced further. (Vitalism) Mechanistic View – vitalism is a myth. All living organisms can be reduced to physical, chemical and mechanical principles. (Müller’s Students, Helmhotz).

Emil Du Bois-Reymond - 1850 Developed very sensitive galvonometer. Was able to measure the role of electrical impulses in neural conductance “No force other than the common physical chemical ones are active within the organism.”

Hermann Ludwig von Helmholtz Physicist Student of Muller’s but disagreed about vitalism. “The conservation of force” Measured the energy and heat produced by a frog’s body and was able to account for it entirely in terms of oxidation of the food the frog injected.

Hermann Ludwig von Helmholtz Speed of neural conductance. (90 feet per second) Established Reaction Time as a measure of Psychological Processing.

Francisus Cornelius Donders Measures the Speed of Choice! 1868 Simple reaction time. Respond to a nonsense sound ki Simple Reaction Time PLUS decisions time. Listen to sounds Ki, Ko, Ku ~ Repeat only Ki Choice took 39 miliseconds!

More Helmholtz … Invented ophthalmoscope – for examining retina. Trichromatic theory of Color Vision

Opponent Process Theory Herring

On the relationship between perception and reality In my opinion, there can be no possible sense in speaking of our ideas except as practical truth. Our ideas of things cannot be anything but symbols, natural signs for things that we learn how to use in order to regulate our movements . . . Hence, there is no sense in asking whether vermillion, as we see it, is really red or whether this is simply an illusion of the senses. The sense of red is the normal reaction of normally formed eyes to light reflected from vermilion . . . That is true entirely without reference to the a special nature of our eye.

Sir Charles Wheatstone (1833)

Psychophysics Ernst Weber – two point threshold.

Might be considered Psychology’s first experiments. Manipulate variable (area of the body tested) Critical distance between compass points. Many contemporaries were arguing that psychology could never be a science!

Was inspired by economic principle that giving a penny to a rich person is not the same as giving a penny to a poor person. Ability to detect change depends on the reference.

Weber’s LAW Thresholds – just noticeable differences. How much does a stimulus need to change before it can be detected. JND/S = k Studied the relationship between the physical and the psychological.

JND depends on the intensity of the standard Weber’s Law I/I = k Change in Intensity divided by Intensity of the standard is a constant. Not “Absolute” but it is predictable.

Gustav Fechner Studies on afterimages led to blindness. - became an invalid, depression. Recovered vision by “taking control over his life”. Used Weber’s JND concept. S = k log R