Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Elizabeth GE Kyonka

Committee Co-Chair

Michael Perone

Committee Member

Natalie Shook


Forgetting is often characterized as maladaptive, but if a cue no longer signals the consequences of a response, then forgetting the previously learned stimulus-response discrimination is adaptive. Pigeons pecked for food in concurrent schedules of reinforcement. The relative frequency of food delivery on each key changed pseudorandomly across sessions with an overnight break in the middle of each session. New sessions began immediately after the last food delivery in the previous session. When the change from one session to the next was not signaled, responses remained under the control of the previous session's ratio of reinforcement. When the session change was signaled by a change in the color of the keylights, control by the ratio from the previous session was diminished. Without interference from past ratios, sensitivity to the ratio of reinforcement was greater in the signaled than the unsignaled condition. This decrease in sensitivity to past ratios marks an example of adaptive forgetting.