Honors Projects


This study examines the relationship between rapid relative reward comparisons and incentive contrast among rats (n=5). Animals were trained to lever-press in order to obtain access to a sucrose solution (concentration used: 1%, 10% or 20% in tap water). These rewards were placed outside an operant box which could be reached through a small hole displaying sessions with mixed comparisons (1v20%, 20v1%) or single sessions (1v1%, 10v10%, 20v20%) that rotated between two spouts containing the pre-randomized order of paired blocks; allowing for comparative analysis between two spouts/concentrations and blocks of responses. Throughout weekly testing each animal experienced a value upshift (positive) or downshifts (negative) relative to another outcome as we examined the incentive contrast effects on behavioral performance. We examined the influence of dynamic comparisons between the two reward outcomes in a repeated measures design with three sessions: a single outcome and a mixed outcome followed by a single outcome session the next day for extinction. Results signified rats experienced negative contrast and scaled their behavioral responses in decreased motivated action to obtain the incentive reward. Positive induction, however, was not obtained and proposes further research and analysis to understand the comparative values and to determine when motivational systems are registered to initiate behavior in animal paradigms. The future direction of this novel design and research area could be essential for investigating interactions between external and internal factors of motivation and reward processing as learning continues to play a role in conditioning and predictive contrast.





First Advisor

Howard Casey Cromwell

First Advisor Department


Second Advisor

Michael Geusz

Second Advisor Department

Biological Sciences

Publication Date

Fall 12-14-2015