LAUSR

BACKGROUND AND AIMS 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 PRISMA protocol, studies were gathered through searches in PsycINFO and PubMed/MEDLINE (published as of May 22, 2018). Searches returned 34 unique studies (aggregate sample N = 2,402; 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, crossover point) in relation to six experimental manipulations (cue exposure, stress/negative affect, reinforcer magnitude, pharmacotherapy, behavioral interventions, opportunity cost). RESULTS Cue exposure (d range = .25 to .44, all ps < .05) and reinforcer magnitude (d = .60; 95% CI = 0.18, 1.01; p < .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 = .18; 95% CI = 0.01, 0.34; p = .03); all other effect sizes for negative affect/stress were nonsignificant, albeit similar in size (d range = .14 to.18). In contrast, pharmacotherapy (d range = -.37 to -.49; ps < .04), behavioral intervention (d = -.36 to -1.13) and external contingency (d = -1.42; CI = -2.30, -.0.54; p = .002) manipulations resulted in a significant decrease in intensity. Moderators (substance type) explained some of the heterogeneity in findings across meta-analyses. CONCLUSIONS 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.