unconditioned stimulus

Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia, Wikipedia.


 [stim´u-lus] (L.)
any agent, act, or influence that produces functional or trophic reaction in a receptor or an irritable tissue.
conditioned stimulus a stimulus that acquires the ability to evoke a given response by repeatedly being linked with another stimulus that naturally evokes that response; see also conditioning.
depolarizing stimulus a stimulus that lowers the resting potential, making the inside of a fiber less negative. In cardiac fibers this means bringing the resting potential from −90 mV to −70 mV.
discriminative stimulus a stimulus associated with reinforcement, which exerts control over a given type of behavior; the subject must discriminate between closely related stimuli and respond positively only with this particular stimulus.
eliciting stimulus any stimulus, conditioned or unconditioned, that elicits a response.
threshold stimulus a stimulus that is just strong enough to elicit a response.
unconditioned stimulus any stimulus that naturally evokes a specific response; see also conditioning.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

un·con·di·tion·ed stim·u·lus

a stimulus that elicits an unconditioned response; for example, food is an unconditioned stimulus for salivation, which in turn is an unconditioned response in a hungry animal. See: classical conditioning.
Farlex Partner Medical Dictionary © Farlex 2012

unconditioned stimulus

n. Psychology
A stimulus that evokes an unconditioned response.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

un·con·di·tioned stim·u·lus

(ŭn'kŏn-dish'ŭnd stim'yū-lŭs)
That which elicits an unconditioned response; e.g., food is an unconditioned stimulus for salivation, which in turn is an unconditioned response in a hungry animal.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

unconditioned stimulus

The stimulus that evokes an UNCONDITIONED RESPONSE.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
The conditioned stimulus may be a property or a by-product of the unconditioned stimulus. For example, if a dog has been deprived of food for a sufficiently long period, the sight of food or the smell of food brings about salivation.
The dotted line at -4.0 s schematically represents the time of the reception of the "telepathic" conditioned stimulus; the dashed line at about -2.75 s represents the response to it; the solid line at 0 s is the unconditioned stimulus onset time; and the large peak beginning at about +1.5 s is the unconditioned response.
Learning for Mowrer was on the stimulus side in the association of the conditioned stimulus with the unconditioned stimulus, but what was changed (learned) were the emotions of hope and fear.
Encoding of the unconditioned stimulus in Pavlovian conditioning.
Via imaging technique, researchers could see that some neurons were activated by the saccharine, or the conditioned stimulus, and the lithium chloride or the unconditioned stimulus activated others.
Abbreviations: CR, conditioned response; CS, conditioned stimulus; EPSP, excitatory postsynaptic potential; IPSP, inhibitory postsynaptic potential; UR, unconditioned response; US, unconditioned stimulus.
In the test phase, the CS is presented with an aversive unconditioned stimulus (US) (e.g., a scrambled footshock).
Skinner (1969) suggested that part of the responses to emotionally arousing classically conditioned stimuli, may include perceptual "conditioned seeing," the tendency to "see familiar objects more readily and easily than unfamiliar objects" and stimuli previously paired with an emotionally eliciting unconditioned stimulus (Skinner, 1953, p.
A possible explanation for these contradictory results may be found in the procedures used to determine contingency awareness between CS and unconditioned stimulus (US).
This is similar to the usual result in Pavlovian conditioning studies, where responses similar to those elicited by the unconditioned stimulus are conditioned to cues they have been repeatedly paired with (see Ayers & Powell, 2002, for a review).
Pairing a conditioned stimulus (CS, e.g., tone or light) with an unconditioned stimulus (US, e.g., food of footshock) results in the development and strengthening of a conditioned response (CR, e.g., salivation or fear) to the CS, in anticipation to the occurrence of the US.
During conditioning, specimens of Hermissenda are presented with a temporal sequence of a light flash as the conditioned stimulus (CS) and mechanical turbulence as the unconditioned stimulus (US).