Since the discovery of the law of effect, psychologists have been investigating a number of the parameters of reinforcing stimuli. The law of effect states that a response is learned, or not learned, depending upon the events (effects) that follow it. To evaluate the aspects of reinforcing stimuli. typically an organism is deprived of food or water and an increase in the probability or speed of a response is noted when small amounts of food or water are made to follow a response. Using this type of paradigm, characteristics of reinforcing stimuli which have been investigated are number of reinforcers, schedule of reinforcement, magnitude of reinforcement, and their effects on rate of responding and resistance to extinction.
Thomson, Phyllis, "An Examination of the Phenomenon of Preference for Bar Pressong over Freeloading" (1966). Honors Projects. Paper 143.