Characterized by the establishing of a response to a stimulus that does not normally evoke the response. The Russian physiologist Ivan Pavlov reported producing a conditioned reflex in dogs during the last part of the 19th century. He used the sight of food (unconditioned stimulus) to induce salivation in the dog (unconditioned response) and fostered a mental connection between the food and the sound of the bell, and the bell’s ring became the conditioned stimulus. It is theoretically possible to classically condition physiological responses to occur uniquely when a subject is deceptive, and this method is one of the promising areas of future research in lie detection. See: Petty & Cacioppo (1981).