Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Kennon A. Lattal.

Committee Co-Chair

Michael Perone

Committee Member

Hayne W. Reese


A multiple chained schedule was used to assess the persistence of fixed and variable response sequences. In one terminal link, a single 4-peck response sequence produced food (Repeat) and in the other terminal link a 4-peck response sequence produced food only if it had been occurring infrequently relative to the other 15 possible responses (Vary). Similar response and reinforcement rates occurred in each terminal link. Identical variable-interval 20-s schedules operated in the initial links preceding each terminal link and lower response rates reliably occurred in the initial link preceding the Vary terminal link. After responding stabilized under the multiple chained schedule, four disruption conditions were employed, one condition in which each pigeon was pre-fed before each session and three conditions in which a variable-time schedule, of three different values, operated during the inter-component intervals that preceded each initial link. During each of the four disruption conditions, response rate in each link of the chained schedule in the Vary component tended to be more persistent, relative to its own baseline level, than response rate in the Repeat component. During the pre-feeding condition, relative to baseline, the amount of variation in the Vary terminal link decreased slightly and the amount of repetition in the Repeat component remained similar. During the variable-time-schedule conditions, the amount of variation in the Vary component remained similar or decreased slightly, relative to baseline, while the amount of repetition in the Repeat component increased considerably. These results extend earlier findings demonstrating that response repetition is more susceptible to environmental disruption than is response variation. The results also suggest that theories of response strength, such as behavioral momentum theory, must take into account different response topographies.