Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Kennon A. Lattal.


To investigate how operant and alternative food arranged by different schedules interact to determine response rates and patterns when the sources of food are the same or different, six experiments were delineated. The effects of the number of food sources were investigated in Experiments 1-4. In Experiments 1 and 2, a variable-interval (VI) schedule was used to program the operant food, while the fixed-time (FT - Experiment 1) or the variable-time (VT - Experiment 2) alternative food was delivered from the same or a different source than that of the operant food. Experiments 3 and 4 were identical to Experiments 1 and 2, except that the operant food was arranged by a differential-reinforcement-of-low-rates (DRL) schedule. The effects of the schedule delivering the alternative food were investigated in Experiments 5 and 6. In Experiment 5, food arranged according to a FT or a VT schedule was superimposed to another source of that delivering the VI-scheduled food. In Experiment 6, the baseline schedule was DRL. Response rates were lower when the operant and alternative food were delivered from different sources, but did not differ systematically depending on the schedule delivering the alternative food. Response patterns were most commonly negatively accelerated when the alternative-food schedule was FT. Peaks during the first tenth of the alternative-food interval were also observed, and were more pronounced when the DRL was used to arrange the operant food. The results are discussed in terms the discriminative properties of the alternative-food presentations, determined by the temporal arrangement of this food, the schedule arranging the operant food, and the separation of alternative- and operant-food sources.