Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Karen G. Anderson

Committee Co-Chair

Barry Edelstein

Committee Member

Brad Humphreys

Committee Member

Claire St. Peter

Committee Member

Constance Toffle


Probability discounting is a measure of risky choice that is correlated with maladaptive behavior and psychological disorders. Benzodiazepines are a class of drug on which relatively little risky-choice research has been conducted, particularly under conditions of chronic drug exposure. Chlordiazepoxide, a standard benzodiazepine, was administered to rats that had been trained to respond on a risky-choice task in which a choice was available between a single food pellet with 100% certainty or three food pellets with probabilities of delivery that decreased across each experimental session. During baseline, responding was sensitive to the programmed contingencies and larger-reinforcer choice decreased as the probability of delivery decreased. Acute administration of chlordiazepoxide dose-dependently increased risky choice. Tolerance to chlordiazepoxide’s effects on larger-reinforcer-choice was observed after chronic drug exposure. The results of the present study indicate that acute chlordiazepoxide can increase risky choice in a probability-discounting task and that tolerance to this effect develops after chronic exposure to the drug. Limitations of the probability-discounting task and its relation to the hypothetical construct “risky choice” are discussed, as are suggestions for additional pharmacological targets and procedural variations for future studies on benzodiazepines, the GABA system, and risky choice.