Reaction


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Related to Reaction: reaction time

reaction

1. opposition to change, esp political change, or a desire to return to a former condition or system
2. a response indicating a person's feelings or emotional attitude
3. Med
a. any effect produced by the action of a drug, esp an adverse effect
b. any effect produced by a substance (allergen) to which a person is allergic the simultaneous equal and opposite force that acts on a body whenever it exerts a force on another body

Reaction

 

in the political sense, resistance to social progress; a political regime established to maintain and strengthen an outmoded social order. Reaction usually manifests itself in the struggle against the revolutionary movement, in the suppression of democratic rights and liberties, in the persecution of progressive political, public, and cultural figures, in mass terror and violence, in racial and national discrimination, and in an aggressive foreign policy. Reaction in its extreme form is fascism.

A reactionary is an adherent of political reaction, a retrograde person, an enemy of social, cultural, and scientific progress.


Reaction

 

in psychology, a behavioral act that takes place in response to a certain stimulus; a voluntary movement that takes place in response to a signal and is influenced by the subject’s idea of the task to be performed. It became necessary to investigate voluntary reaction after it was discovered that astronomers attempting to note the moment a star passed through a meridian were giving different figures. F. Bessel, who discovered this phenomenon, conducted an experiment in 1823 to measure reaction times of human beings to stimuli. The measurement of speed, intensity, and course of reactions created psychometrics as a branch of psychology with a special method of investigation—the method of reaction. Pioneers in this field included F. Donders of Denmark and W. Wundt, L. Lange, and N. N. Lange. Reaction was also studied by the Soviet psychologist K. N. Kornilov, the founder of reactology.

There are two basic types of reactions: simple and complex. In a simple reaction, a person quickly responds with a movement (motor and sensory reaction) to a single prearranged signal. In a complex reaction, when various signals are randomly given, a person responds to only one of them (discrimination reaction) or to all of them, but with various movements (choice reaction). The study of reaction has made it possible to formulate a number of principles of applied psychology, such as Hick’s law, which states that reaction time increases with an increase in the number of stimuli presented for discrimination.

REFERENCES

Wundt, W. Osnovy fiziologicheskoi psikhologii, fascs. 1–16. St. Petersburg, 1908–14.
Inzhenernaia psikhologiia za rubezhom. Moscow, 1967. Pages 408–24. (Collection of articles translated from English.)
See also references under .

V. I. MAKSIMENKO

reaction

[rē′ak·shən]
(control systems)
(mechanics)
The equal and opposite force which results when a force is exerted on a body, according to Newton's third law of motion.
(nuclear physics)
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