The adjusting-amount delay-discounting task: at each of seven delays, five choices between an amount now and 1,000 later narrow down the indifference point, giving a discounting curve, its area and a discount rate.
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Task parameters
Koffarnus & Bickel (2014): 1,000. Each delay starts at 500 now vs. 1000 later; the immediate amount then moves by 250, then by half the previous step.
Euro by default, with the published amounts unchanged, as in the euro version of Mas-Cuesta et al. (2022); the original studies used US dollars.
Koffarnus & Bickel (2014): seven delays in random order (1 day, 1 week, 1 month, 6 months, 1 year, 5 years, 25 years), five choices per delay, the sides assigned at random on each trial; 35 choices. The adjusting-amount procedure goes back to Du, Green & Myerson (2002). Practice: 10 choices that do not adjust (Frye et al., 2016); their amounts and delays, apart from Frye's example of 10 now vs. 100 in a month, are a lab choice. About 3 minutes.
Outputs: the indifference point at each delay, i.e. the immediate amount after a final adjustment (the amount a 6th choice would offer; Frye et al., 2016), one of 32 evenly spaced values; the area under the curve with delays and amounts as shares of the longest delay and the delayed amount (Myerson, Green & Warusawitharana, 2001); k of the hyperbola V = A / (1 + kD) fitted to the indifference points by least squares (Koffarnus & Bickel, 2014), with ln(k) and R²; and whether the data are systematic by Koffarnus & Bickel's check (the 1-day point at least 10% of the amount above the 25-year point; at most one point more than 20% above the one before).
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Simulated participant view
The adjusting-amount delay-discounting task: at each of seven delays, five choices between an amount now and 1,000 later narrow down the indifference point, giving a discounting curve, its area and a discount rate.
No data is recorded
Two option cards per choice: an amount now and 1,000 after a delay. The immediate amount moves up after a "later" choice and down after a "now" choice, by 250, then by half the previous step. The sides of the options are random on each trial.
Useful when a study needs indifference points across delays, e.g. to compare discounting curves, compute the area under the curve, or fit discounting models, in addiction, impulsivity and decision-making research.
Less suitable for very frequent EMA: for a quick repeated measure use the 5-trial adjusting delay task; for a fixed, widely normed questionnaire use the Monetary Choice Questionnaire.
The defaults follow Koffarnus & Bickel (2014): 1,000 later vs. 500 now on the first choice at each of seven delays (1 day, 1 week, 1 month, 6 months, 1 year, 5 years, 25 years) in random order, five choices per delay (35 in all), and the sides assigned at random on each trial. Ten practice choices that do not adjust come first (Frye et al., 2016). The procedure goes back to Du, Green & Myerson (2002). Amounts are shown as published in the chosen currency (euro by default, as in Mas-Cuesta et al., 2022).
The indifference point at a delay is the immediate amount after a final adjustment, i.e. the amount a sixth choice would offer (Frye et al., 2016): one of 32 evenly spaced values between 0 and 1,000. The area under the curve uses delays as a share of 25 years and amounts as a share of the delayed amount; 1 means no discounting and values near 0 steep discounting. k is the least-squares fit of V = A / (1 + kD) to the indifference points (D in days). Data that fail the systematic-data check are often excluded.
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