The priming effect of rewarding brain stimulation depends on both the cost and strength of reward

Receipt of an intense reward boosts motivation to work for more of that reward. This phenomenon is called the priming effect of rewards. Using a novel measurement method, we show that the priming effect depends on the cost, as well as on the strength, of the anticipated reward. Previous research on the priming effect of electrical brain stimulation utilized a runway paradigm in which running speed serves as the measure of motivation. In the present study, the speed with which a two-lever response chain was executed in a standard operant-conditioning chamber served as the measure of motivation. In a second experiment, we introduced a modification of our measurement method that entails self-administered priming stimulation and alternating blocks of primed and unprimed trials. Reliable, consistent priming effects of substantial magnitude were obtained in the modified paradigm, which is closely analogous to the runway paradigm.