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Origins of Randomization in Experimental Design”

Early experimental psychology[edit]

See also: Psychophysics

Wilhelm Wundt[edit]

Main article: Wilhelm Wundt

Experimental psychology emerged as a modern academic discipline in the 19th century when Wilhelm Wundt introduced a mathematical and experimental approach to the field. Wundt founded the first psychology laboratory in Leipzig, Germany.[2] Other experimental psychologists, including Hermann Ebbinghaus and Edward Titchener, included introspection among their experimental methods.

Charles Bell[edit]

Main article: Charles Bell

Charles Bell was a British physiologist, whose main contribution was research involving the nervous system. He wrote a pamphlet summarizing his research on rabbits. His research concluded that sensory nerves enter at the posterior (dorsal) roots of the spinal cord and motor nerves emerge from the anterior (ventral) roots of the spinal cord. Eleven years later, a French physiologist Francois Magendie published the same findings without being aware of Bell’s research. Due to Bell not publishing his research, the discovery was called the Bell-Magendie law. Bell’s discovery disproved the belief that nerves transmitted either vibrations or spirits.

Ernst Heinrich Weber[edit]

Main article: Ernst Heinrich Weber

Weber was a German physician who is credited with being one of the founders of experimental psychology. His main interests were the sense of touch and kinesthesis. His most memorable contribution is the suggestion that judgments of sensory differences are relative and not absolute. This relativity is expressed in “Weber’s Law,” which suggests that the just-noticeable difference, or jnd is a constant proportion of the ongoing stimulus level. Weber’s Law is stated as an equation:{\displaystyle {\frac {\Delta I}{I}}=k,}

{\frac  {\Delta I}{I}}=k,
I\!
\Delta I\!
\Delta I\!

where {\displaystyle I\!} is the original intensity of stimulation, {\displaystyle \Delta I\!} is the addition to it required for the difference to be perceived (the jnd), and k is a constant. Thus, for k to remain constant, {\displaystyle \Delta I\!} must rise as I increases. Weber’s law is considered the first quantitative law in the history of psychology.[3]