stimulus

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n., pl. -li (-lī').

1. Something causing or regarded as causing a response.
2. An agent, action, or condition that elicits or accelerates a physiological or psychological activity or response.
3. Something that incites or rouses to action; an incentive: “Works which were in themselves poor have often proved a stimulus to the imagination” (W.H. Auden).

[Latin, goad.]

noun

1. Something that causes and encourages a given response: encouragement, fillip, impetus, impulse, incentive, inducement, motivation, prod, push, spur, stimulant, stimulation, stimulator. See cause/effect.
2. Something that incites especially a violent response: goad, incitation, incitement, instigation, provocation, trigger. See cause/effect.

n

Definition: provocation
Antonyms: deterrent, discouragement, hindrance, tranquilizer

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(stim′yōōlus)
n

A chemical, thermal, electrical, or mechanical influence that changes the normal environment of irritable tissue and creates an impulse.

p1. stimuli

1. Any factor inside or outside an organism, but external to a sensory receptor. which initiates activity of some kind.

2. An internal or external event that tends to alter the behaviour of an organism.

plur. stimuli (stim-yuh-leye)

An action, condition, or person that provokes a response, especially a conditioned response.

Stimuli are patterns of energy received by the senses; they evoke behaviour and are the basis of perception. Even so, they may not be noticed or experienced, or they may be only part of what we experience and accept as signals or data for behaviour and perception. In particular, retinal images may be thought of as patterns of energy from the external world, but we do not see them. We see objects, partly as the result of signals from these optical stimuli and partly from our knowledge of what objects are like.

The role of stimuli is rather differently described in various biological and psychological accounts. 'Stimulus– response' theories for behaviour emphasize the importance of received stimuli rather than internal processes — a line of argument most radically worked out in behaviourism (see conditioning). Such an approach, perhaps, had its initial plausibility as a psychological theory from observations of highly predictable tropisms (responses to or away from light, chemical concentrations, etc.) found in many lower organisms. The German-born American physiologist Jacques Loeb (1859–1924) explained the 'forced movements' in simple animals in terms of the 'tonus hypothesis', namely that the muscular tone on each side of the body is affected by the relative intensity of signals from paired sense organs, especially the eyes, the animal moving towards the side having the strongest muscular tension. This view has been largely abandoned as a theory of tropisms in animals, but a similar explanation is accepted for plants as they grow towards the light, or grow upright by geotropisms. It is believed that, whereas stimuli can have quite direct effects on plants, their effects on even simple animals are seldom direct, as they are 'read' or interpreted according to the situation and the needs of the animal.

Stimuli can however evoke reflexes which may be complex, and were thought by the behaviourists to be the building-blocks of all behaviour (even language). Their role and characteristics were discovered especially by Pavlov and Sherrington. Although basic for the internal functions of all animals (with internal stimuli as for proprioception) and for immediate responses to external events (signalled by the various senses of touch, hearing, vision, etc.), present-day cognitive psychology shows that 'higher' behaviour is not controlled directly by stimuli; but, rather, by what is 'postulated' by the brain as the cause of the stimuli. Stimuli become evidence for what is out there, read from knowledge of objects, and how they interact, and what they might do or be used for. So 'top-down' neural processes modulate effects of stimuli and give them meaning.

(Published 1987)

See also psychophysics.

— Richard L. Gregory

Bibliography
• Jeannerod, M. (1997). The Cognitive Neuroscience of Action.
• Loeb, J. (1918). Forced Movements, Tropisms and Animal Conduct.
• Sherrington, C. (1947). The Integrative Action of the Nervous System.

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Pl. stimuli [L.] any agent, act, or influence that produces functional or trophic reaction in a receptor or an irritable tissue.

• conditioned s. — a neutral object or event that is psychologically related to a naturally stimulating object or event and which causes a conditioned response. See also conditioning.
• discriminative s. — a stimulus associated with reinforcement, which exerts control over a particular form of behavior; the subject discriminates between closely related stimuli and responds positively only in the presence of that stimulus.
• eliciting s. — any stimulus, conditioned or unconditioned, which elicits a response.
• s. generalization — in learning by animals stimuli tend to be grouped together, the reactions lacking the discrimination of the higher mammals.
• s. response coupling — coupling of the neural or endocrine stimulus to the cellular response.
• structured s. — a well-organized and unambiguous stimulus, the perception of which is influenced to a greater extent by the characteristics of the stimulus than by those of the perceiver.
• threshold s. — a stimulus that is just strong enough to elicit a response.
• unconditioned s. — any stimulus that is capable of eliciting an unconditioned response. See also conditioning.
• unstructured s. — an unclear or ambiguous stimulus, the perception of which is influenced to a greater extent by the characteristics of the perceiver than by those of the stimulus.

IN BRIEF: The thing that makes something or someone more active.

Pavlov's findings were that some animals learned more quickly if rewarded each time they showed the right response, while others learned more quickly when the penalty for not learning was a painful stimulus. — Joost Meerloo

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Dansk (Danish)
n. - stimulans, drivfjeder, spore

Nederlands (Dutch)
prikkel, stimulus, stimulans

Français (French)
n. - (Physiol) stimulus, (fig) impulsion, (fig) stimulant

Deutsch (German)
n. - Stimulus, Reiz, Ansporn

Ελληνική (Greek)
n. - (φυσιολ.) ερέθισμα (των αισθήσεων), (μτφ.) κίνητρο, έναυσμα

Italiano (Italian)
stimolo, sprone, incentivo, pungolo

Português (Portuguese)
n. - estímulo (m)

Русский (Russian)
стимул, побудительная причина, стимулирующее, возбуждающее воздействие, раздражитель

Español (Spanish)
n. - estímulo, incentivo

Svenska (Swedish)
n. - stimulans, eggelse, drivfjäder, retning

中文（简体）(Chinese (Simplified))
刺激, 刺激品, 激励

中文（繁體）(Chinese (Traditional))
n. - 刺激, 刺激品, 激勵

한국어 (Korean)
n. - 자극, 격려 , 흥분제

日本語 (Japanese)
n. - 刺激, 激励

العربيه (Arabic)
‏(الاسم) حافز, دافع, منشط‏

עברית (Hebrew)
n. - ‮גורם ממריץ, דחיפה‬

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