Tests of an indifference rule in variable‐delay and double‐reward choice procedures with humans
The way you frame delay-choice questions changes the discounting curve you get from adult humans online.
01Research in Context
What this study did
The team ran two online choice games with the adults.
In one game, people picked between $50 now or $100 after waits that changed every trial.
In the other game, people picked between $50 now or double that amount later while the wait stayed fixed.
All tasks were done on computers at home.
What they found
The double-reward game gave neat hyperbolic curves that fit Mazur’s equation.
The changing-delay game did not fit the same curve.
Same people, same money, but the task shape changed the discounting pattern.
How this fits with other research
Nickerson et al. (2015) saw the same thing: when people must sit and wait at the screen, they act more impulsive.
Odum et al. (2020) reviewed 200 papers and found money is discounted less steeply than food or smokes; our task differences are on top of that baseline.
Holt et al. (2018) got clean curves with pigeons using steady delays, matching our double-reward condition and showing the procedure, not the species, drives the curve.
Why it matters
If you assess delay discounting for treatment planning, keep the task format the same every time. A simple switch from fixed to variable delays can make a client look more impulsive than they are. Pick one procedure and stick with it.
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02At a glance
03Original abstract
Four hundred and fifty participants were recruited from Amazon Mechanical Turk across 3 experiments to test the predictions of a hyperbolic discounting equation in accounting for human choices involving variable delays or multiple rewards (Mazur, 1984, 1986). In Experiment 1, participants made hypothetical choices between 2 monetary alternatives, 1 consisting of a fixed delay and another consisting of 2 delays of equal probability (i.e., a variable-delay procedure). In Experiment 2, participants made hypothetical monetary choices between a single, immediate reward and 2 rewards, 1 immediate and 1 delayed (i.e., a double-reward procedure). Experiment 3 also used a double-reward procedure, but with 2 delayed rewards. Participants in all 3 experiments also completed a standard delay-discounting task. Finally, 3 reward amounts were tested in each type of task ($100, $1000, and $5000). In the double-reward conditions (Experiments 2 and 3), the results were in good qualitative and quantitative agreement with Mazur's model (1984, 1986). In contrast, when participants made choices involving variable delays (Experiment 1), there was relatively poor qualitative and quantitative agreement with this model. These results, along with our previous findings, suggest the structure of questions in hypothetical tasks with humans can be a strong determinant of the choice pattern.
Journal of the Experimental Analysis of Behavior, 2019 · doi:10.1002/jeab.521