The present experiment was designed to assess whether stimuli correlated with rich and lean fixed-ratio schedule components would function as conditioned reinforcers and conditioned punishers, respectively. Pigeons responded on a mixed schedule with fixed-ratio components leading to large or small food reinforcers. Pecks on either of two observing keys converted the mixed schedule to a multiple schedule by turning on a color associated with the current component. The stimulus consequences of the observing responses were manipulated across conditions. Pecks on one observing key produced the rich stimulus and the lean stimulus whereas pecks on the other observing key produced only the rich or the lean stimulus. The stimulus correlated with the large reinforcer functioned as a conditioned reinforcer---it maintained observing behavior---whereas the stimulus correlated with the small reinforcer did not. There was no evidence that the stimulus correlated with the small reinforcer functioned as a conditioned punisher
