Comparison between two measures of delay discounting in smokers.

Agreement between computer and questionnaire measures of delay discounting in smokers was compared. Correlations between measures for small, medium, or large rewards were significant. Log k values decreased as the reward delay increased, with values lower for the computer task than the questionnaire, with significant differences for small rewards. The 2 measures were related to smoking rate but not to age, gender, or obesity. The Bland-Altman test of agreement indicated large within-subject differences in k values between the 2 measures. The size of the difference between the log k values and magnitude of the log k values were positively related. Results suggest k values from the 2 measures are related but may not be used interchangeably.