Abstract
Five out of six rats, pressing a lever for food reinforcement, showed differential rates of responding that were correlated with the presence of a buzzer, under conditions where the buzzer might have been assumed to be neutral. The effect was demonstrated when the presence versus absence of the buzzer distinguished the components of Mult FI 2 min FI 2 min, as well as when the buzzer was present throughout entire sessions of simple FI 2 min for n/2 of every n such sessions. The cause of the phenomenon was not determined.