Characterizing the reinforcing value of tobacco using a cigarette purchase task: An item response theory approach.

The Cigarette Purchase Task (CPT) affords a high-resolution index of the reinforcing efficacy of nicotine. Although a high number and steep progression of prices have traditionally been used, attention is now placed on developing brief measures of this task. This study sought to assess the psychometric properties of a brief CPT for assessing cigarette demand in treatment-seeking smokers with and without depressive symptoms. The study sample comprised 360 participants (210 with and 150 without depressive symptomatology). We tested the effect of different CPT price densities (14-19) on the variation of CPT indices and provided a thorough assessment of its reliability using 2 different approaches: the classical test theory and item response theory models. Reliability analyses indicated that the 14-item CPT performed the best in terms of reliability across study samples. The CPT's information functions for this shortened version yielded the highest precision at medium levels of the measured construct (for theta values between -0.4 and 0.4). O