Due to its relevance to human diseases and behavioral disorders, delay discounting has become a topic of interest to researchers across a wide range of scientific disciplines. The within-sessions procedure is the most widely used procedure to assess delay discounting in nonhumans (Madden & Bickel, 2015). To date, most within-sessions procedures have been designed specifically for use with rats. However, mice are the organism of choice in biomedical and genetic research. Interdisciplinary research requires the standardization of assessments for mice. Only a few published studies have utilized the within-sessions procedure with mice, these have yielded disparate results. The present experiment investigated the impact of delay progression, number of trainings and delay length on resultant performance of Balb-c mice on the within-sessions impulsive choice test. The findings suggest that each of these factors influence performance. Mice show greater preference for the large reward and greater sensitivity to delay lengths when delays are gradually increased over time as compared to when they are not. Mice show a greater sensitivity to delay length when delays are kept shorter (maximum delay of 8 s) verses longer (maximum delay of 12 s). Finally, the number of trainings that animals receive impact resultant performance. The present data support the notion that the within-sessions procedure must be specifically calibrated for use with mice and the findings herein can help to guide further development in this important area of research
