Brain stimulation reinforcement: implications of an electrode artifact.

from CRF to the schedule (12). Accordingly, it is not BSR per se that makes schedule control difficult, but its property of being applied in the last link of a one-link chain. Other applied reinforcers pose similar problems in rats and ducklings (13) as well as humans (14). Carlisle (15) found that rats pressing to turn on a heat lamp reinforcer in a cold chamber performed well on a CRF schedule, but poorly on an intermittent schedule unless a chaining procedure was used. Whereas most of the experiments since 1958 in which the older electrode and plug assembly was used remain valid, conclusions from those in which information about BSR onset was varied should be questioned, because the information would act as an SD for postural adjustment leading to increased reinforcement. Some examples of those experiments follow: Stein's (16) conclusion that stimulus need not be an SD for it to be a conditioned reinforcer. The finding by Steiner et al. (17) that a pattern of BSR which rats produce in a self-stimulation test is aversive when "played back" independent of behavior; Faircloth's (18) conclusion that BSR is more reinforcing when it is self-initiated; Bollinger and Gerall's (19) finding of a decrease in brain-electrode impedance associated with the acquisition of self-stimulation; and my conclusion with LoLordo (20) that rats prefer signaled to unsignaled BSR. MICHAEL B. CANTOR* Department ofPsychology, Columbia University, New York 10027