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1. any drug, agent, electrical impulse, or other factor able to cause a response in an organism
2. an object or event that is apprehended by the senses
3. Med a former name for stimulant



something that excites to action and motivates behavior. The concept of stimulus is characteristic primarily of those trends in psychology that base behavior analysis on the stimulus-response correlation (classical psychophysics and especially behaviorism, as well as neobehaviorism). The term “stimulus” is also retained in some psychological concepts that in essence supersede the stimulus-response correlation. Thus, for example, in the Würzburg school, a task or an awareness of a goal is considered to be a stimulus. In this case, the term “stimulus” is almost metaphorical. Even further from the term’s original meaning is the treatment it receives in the cultural and historical conceptions of L. S. Vygotskii, who established a functional difference between stimulus objects, at which action is directed, and stimulus means, by which action is accomplished. According to Vygotskii, signs serve as stimulus means.

In sociopsychological studies a distinction is sometimes made between motives as internal excitations and stimuli as external excitations to action (see Chelovek i ego rabota [collection], 1967, pp. 38–39).



(control systems)
A signal that affects the controlled variable in a control system.
An agent that produces a temporary change in physiological activity in an organism or in any of its parts.
References in periodicals archive ?
Because olfactory receptor cells are principally designed for detecting changes in chemical stimulus environments (Borroni and Atema 1988, Gomez and Atema 1996), it follows that the critical factor regulating olfactory responses, expressed at both the cellular and organismic levels, should be the change in flux.
Although these devices increase investigator control over chemical stimulus environments, they frequently create a rtificial patterns of contact between the experimental subject and signal molecules.
Sulfide as a chemical stimulus for deep-sea hydrothermal vent shrimp.
For experimental trials, the chemical stimulus (squid, mussel, or clam) was placed in the tank before the sea star was added.
In chemical stimulus trials, five stimulus sources were used: squid flesh (a broad-based amino acid source), whole live clam and mussel (potential prey items), and cracked clam and mussel (wounded potential prey items).
Investigators studying chemoreceptive behavior of marine organisms are faced with a challenge: at macroscopic scales, the chemical stimulus environment in flowing water is very difficult to control.
This procedure is meant to simplify the identification of response, but the results may be misleading when the primary effect of a chemical stimulus is to modify the locomotory behavior of animals already aroused, rather than to initiate foraging or feeding from the quiescent state.
Mechanisms of plume-following behavior, therefore, arise in response to chemical stimulus distributions, as determined by the specific fluid dynamic environments in which animals must naturally navigate.

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