Abstract
Adult female squirrel monkeys, Saimiri sciureus, were conditioned on a fixed-interval 10-min. schedule of Noyes 190-mg food pellets until steady states were recorded. Chronic, sublethal doses of dimethylmercury were then administered via the intraperitoneal route prior to each experimental session. Physiologically normal saline was administered IP during control sessions. Following the chronic series, one acute dose of mercury was administered to each S. As transitions between the chronic doses and the acute dose occurred, proportionate rate changes typical of the effects of variable-interval scheduling were observed, even though the fixed-interval schedule contingencies remained constant throughout the investigation. The results are explained as a function of sensory-motor disruptions due to the entrance of organic mercury into the brain and spinal cord.