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a signal that causes a conditioned reflex; it may be any stimulus of an organism’s external or internal environment that is perceived by the sensory organs and that causes excitation in the cerebral cortex.
The conditioned stimulus precedes an unconditioned stimulus or coincides with it. Natural conditioned stimuli are used in unconditioned reinforcement; examples are the sight and smell of food. Artificial conditioned stimuli are more varied and do not have a direct relationship to the properties of the unconditioned stimulus; they become positive or negative conditioned signals only when a conditioned reflex is being developed. Conditioned stimuli that are indirect signals of the food-related, defensive, and sexual reflexes are of great importance in the adaptive behavior of animals.