title: Syntax for calculation of discounting indices from the monetary choice questionnaire and probability discounting questionnaire.
abstract: The 27-item Monetary Choice Questionnaire (MCQ; Kirby, Petry, & Bickel, 1999) and 30-item Probability Discounting Questionnaire (PDQ; Madden, Petry, & Johnson, 2009) are widely used, validated measures of preferences for immediate versus delayed rewards and guaranteed versus risky rewards, respectively. The MCQ measures delayed discounting by asking individuals to choose between rewards available immediately and larger rewards available after a delay. The PDQ measures probability discounting by asking individuals to choose between guaranteed rewards and a chance at winning larger rewards. Numerous studies have implicated these measures in addiction and other health behaviors. Unlike typical self-report measures, the MCQ and PDQ generate inferred hyperbolic temporal and probability discounting functions by comparing choice preferences to arrays of functions to which the individual items are preconfigured. This article provides R and SPSS syntax for processing the MCQ and PDQ. Specifically, for the MCQ, the syntax generates k values, consistency of the inferred k, and immediate choice ratios; for the PDQ, the syntax generates h indices, consistency of the inferred h, and risky choice ratios. The syntax is intended to increase the accessibility of these measures, expedite the data processing, and reduce risk for error.
authors.affiliation: Department of Psychology, University of Georgia. jgray4@uga.edu.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Gray
authors.affiliation: Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Amlung
authors.affiliation: Department of Psychiatry, University of California, San Diego.
authors.forename: Abraham A
authors.initials: AA
authors.lastname: Palmer
authors.affiliation: Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton.|Homewood Research Institute, Homewood Health Centre.
authors.forename: James
authors.initials: J
authors.lastname: MacKillop
mesh_terms: D002755:Choice Behavior; D065786:Delay Discounting; D006801:Humans; D011336:Probability; D012201:Reward; D011795:Surveys and Questionnaires
keywords: MCQ; PDQ; delay discounting; probability discounting; syntax