Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Karen G Anderson

Committee Co-Chair

Melissa Blank

Committee Member

Elizabeth Kyonka


Lewis (LEW) and Fischer 344 (F344) rats are two genetically different strains that differ in impulsive choices made in a delay-discounting task. An operational definition of impulsive choice is a choice of a smaller-sooner reinforcer over a larger-later reinforcer. Research using LEW and F344 rats has housed rats singly. Studies have shown that paired housing influences impulsive choice, but it is not known if paired housing affects impulsive choice in the LEW and F344 strains specifically. The present study compared impulsive choice in pair-housed LEW and F344 rats to archival data from singly housed LEW and F344 rats. Impulsive choices were measured at baseline and after d-amphetamine (d-AMP) administration. In singly housed rats, LEW rats made more impulsive choices at baseline compared to F344 rats. In addition, impulsive choices decreased for LEW rats but increased or did not change for F344 rats when d-AMP was administered. The present study found the reverse in pair-housed rats: F344 rats made more impulsive choices at baseline than LEW rats. In addition, d-AMP either increased or did not affect impulsive choices in LEW rats, but decreased impulsive choices in F344 rats. Though a small sample size limits the conclusions that may be drawn from the data, this study demonstrates that environmental variables, particularly social conditions, may affect impulsive choice in the LEW and F344 strains differently. In addition, effects of d-AMP on impulsive choice are likely baseline-dependent, evidenced by the occurrence of decreases in impulsive choice in response to d-AMP for rats making larger numbers of baseline impulsive choices in both studies.