Validity and reliability of the cigarette purchase task when participant cigarette consumption is unconstrained

Hypothetical purchase tasks offer effective and efficient methods to assess the reinforcing value of various substances, including cigarettes. The purpose of the present study is to examine the validity and reliability of the Cigarette Purchase Task (CPT) in an experimental arrangement in which participants were receiving free cigarettes. Critical to the validity of the CPT is that those who smoke can accurately estimate how much they would smoke under varying economic constraints. Participants (N = 9) were provided free study cigarettes for 8 weeks. Participants completed the CPT once weekly. To examine the validity of the five CPT demand indices (i.e., demand intensity, P_max, O_max, breakpoint, and α), we used a simple linear regression stratified by session number to model which of the five CPT demand indices were associated with the number of cigarettes smoked per day during Week 1 of the experiment. Significant associations in the hypothesized direction were noted across the five CPT indices, with the evidence for validity greatest for intensity, followed by O_max, P_max, breakpoint, and α. To examine CPT test-retest reliability, we estimated interclass correlation coefficients between Sessions 1 and 4 and Sessions 5 and 8. All but one interclass correlation coefficient supported "good" or "excellent" reliability, with the only exception seen with the α index between Sessions 1 and 4, which was moderate reliability. Collectively, these results provide evidence supporting the construct validity and temporal stability/reliability of the CPT demand indices under conditions of limited economic constraint. (PsycInfo Database Record (c) 2025 APA, all rights reserved).