WITHIN-SESSION RESPONSE RATES WHEN REINFORCEMENT RATE IS CHANGED WITHIN EACH SESSION

Three pigeons pecked keys and 5 rats pressed levers for food delivered on variable-interval schedules. During baseline conditions, subjects responded on a variable-interval 40-s schedule throughout the session. During experimental conditions, the programmed rate of reinforcement changed every 10 min in the 50-min sessions. When rats served as subje cts, Herrnstein's (1970) hyperbolic equation provided a good descripti on of the relation between rate of responding during a 10-min interval and the rate of reinforcement obtained during that interval. Respondi ng, measured over 10-min blocks, was also approximately equally sensit ive to changes in the programmed rate of reinforcement at all times in the session. Herrnstein's equation provided a poorer description of t he changes in responding when pigeons served as subjects. Differences in experimental experience or differences in the absolute rates at whi ch subjects responded may have contributed to the differences in resul ts for these different species.