Delay discounting, which refers to the phenomenon that rewards decrease in subjective value as the delay associated with their receipt increases, is a paradigm that has been used extensively in substance abuse research to understand impulsive decision making. One common measure to assess delay discounting is the Monetary Choice Questionnaire (MCQ) developed by Kirby, Petry, and Bickel (1999). While the MCQ has great utility because of its simplicity and brief administration time, it is possible that the MCQ produces a ceiling effect in estimating delay discounting parameters in highly impulsive individuals. In the present study, we adapted the MCQ to attempt to address this ceiling effect by extending the original scale with 9 items, and we then compared scores on the original MCQ with the extended MCQ in a sample of active cocaine users. The ceiling effect, while observed in the original MCQ scores for over a quarter of the sample, was largely eliminated with the extended scale. Highly impulsive participants, whose scores on the extended scale exceeded the highest possible score on the original scale, had higher levels of sensation seeking compared to other participants, but not trait impulsivity. The extended MCQ may be useful in populations with high rates of impulsivity, where the original measure may underestimate discounting rates due to a ceiling effect.
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