Reinforcing value, an index of motivation for a drug, is commonly measured using behavioral economic purchase tasks. State-oriented purchase tasks are sensitive to phasic manipulations, but with heterogeneous methods and findings. The aim of this meta-analysis was to characterize the literature examining manipulations of reinforcing value, as measured by purchase tasks and multiple-choice procedures, to inform etiological models and treatment approaches METHODS: A random-effects meta-analysis of published findings in peer-reviewed articles. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol, studies were gathered through searches in PsycINFO and PubMed/MEDLINE (published 22May 2018). Searches returned 34 unique studies (aggregate sample n=2402; average sample size=68.94) yielding 126 effect sizes. Measurements included change (i.e. Cohen's d) in six behavioral economic indices (intensity, breakpoint, Omax , Pmax , elasticity, cross-over point) in relation to six experimental manipulations (cue exposure, stress/negative affect, reinforcer magnitude, pharmacotherapy, behavioral interventions, opportunity cost). Cue exposure (d range=0.25-0.44, all Ps<0.05) and reinforcer magnitude [d=0.60; 95% confidence interval (CI)=0.18, 1.01; P<0.005] manipulations resulted in significant increases in behavioral economic demand across studies. Stress/negative affect manipulations also resulted in a small, significant increase in Omax (d=0.18; 95% CI=0.01, 0.34; P=0.03); all other effect sizes for negative affect/stress were non-significant, albeit similar in size (d range=0.14-0.18). In contrast, pharmacotherapy (d range=-0.37 to -0.49; Ps<0.04), behavioral intervention (d=-0.36 to -1.13) and external contingency (d=-1.42; CI=-2.30, -0.54; P=0.002) manipulations resulted in a significant decrease in intensity. Moderators (substance type) explained some of the heterogeneity in findings across meta-analyses. In behavioral economic studies, purchase tasks and multiple-choice procedures appear to provide indices that are sensitive to manipulations found to influence motivation to consume addictive substances in field experiments.
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