Nailing Down the Perceptual Explanation of the Date/Delay Effect in Temporal Discounting

The term temporal discounting describes people's often-observed preference for smaller, but sooner (SS) rewards over larger, but later (LL) rewards. This discounting effect is reduced when the time period to wait for the LL is expressed as an end date (e.g., April 3) rather than a delay (e.g., 80 days). Several explanations of this Date/Delay Effect have been put forward, one of which is the differential time estimation hypothesis claiming that the duration expressed as an end date is perceived as shorter. The few empirical demonstrations in favor of this view used rating scales for subjective duration judgments that have some methodological shortcomings. To achieve a more comprehensive approach, an objective psychophysical discrimination task was used in the current study. In two online experiments (N = 140 and N = 80), participants made timed decisions comparing which of two periods (one expressed as a date, one expressed as a delay in days) was shorter (or longer). The psychometric functions not only showed a clear bias to view the dates as shorter than the delays, but it could be quantified by estimating the point of subjective equality (PSE) which conformed to a delay-to-date ratio of about 83% and 93% in Studies 1 and 2, respectively. Data and analysis scripts are available at https://osf.io/gmkaj/.