Alternate versions of a fixed-choice, delay-discounting assessment for repeated-measures designs

Delay discounting, reflected in the tendency to prefer immediate rewards over delayed rewards, is associated with most forms of problematic substance use. When assessed multiple times to examine within-individual changes, for example, following acute drug administration or an intervention, shifts in delay discounting simply because of repeated assessment is a concern, particularly when the assessment task is identical. This may be true for the Monetary Choice Questionnaire (MCQ), a widely used, fixed-item assessment of delay discounting. The present research examined possible within-individual difference/equivalence of MCQ indices at test/retest. This was contrasted with within-individual difference/equivalence when using an alternate version of the MCQ at retest, specifically developed to maintain the assessment structure and scoring of the original MCQ but with different choice items. Eighty-four participants completed delay discounting at test and retest with a 1-week interval; participants were randomized to complete the MCQ at both test and retest (MCQ/MCQ; n = 43) or complete the MCQ at test and an alternate version of the MCQ at retest (MCQ/MCQ-A; n = 41). Conventional hypothesis testing indicated no significant changes in delay discounting in the MCQ/MCQ condition or MCQ/MCQ-A condition. However, equivalence analysis, which is able to established whether scores are statistically equivalent, indicated that test/retest scores were not equivalent in some cases. Specifically, only 1 magnitude in the MCQ/MCQ condition was equivalent at test/retest, whereas 2 magnitudes in the MCQ/MCQ-A condition were equivalent at test/retest. (PsycINFO Database Record (c) 2018 APA, all rights reserved).