Reliability of the Discounting Inventory: An extension into substance-use population

Recent research introduced the Discounting Inventory that allows the measurement of individual differences in the delay, probabilistic, effort, and social discounting rates. The goal of this investigation was to determine several aspects of the reliability of the Discounting Inventory using the responses of 385 participants (200 non-smokers and 185 current-smokers). Two types of reliability are of interest. Internal consistency and test-retest stability. A secondary aim was to extend such reliability measures beyond the non-clinical participant. The current study aimed to measure the reliability of the DI in a nicotine-dependent individuals and non–nicotine-dependent individuals. It is concluded that the internal consistency of the DI is excellent, and that the test–retest reliability results suggest that items intended to measure three types of discounting were likely testing trait, rather than state, factors, regardless of whether “non-smokers” were included in, or excluded from, the analyses (probabilistic discounting scale scores being the exception). With these cautions in mind, however, the psychometric properties of the DI appear to be very good.