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Four-hundred and fifty participants were recruited from Amazon Mechanical Turk across three 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 two monetary alternatives, one consisting of a fixed delay and another consisting of two delays of equal probability (i.e., a variable-delay procedure). In Experiment 2, participants made hypothetical monetary choices between a single, immediate reward and two rewards, one immediate and one delayed (i.e., a double-reward procedure). Experiment 3 also used a double-reward procedure, but with two delayed rewards. Participants in all three experiments also completed a standard delay-discounting task. Finally, three 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.

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McKerchar, T. and Mazur, J.E. (April 2019) "Tests of an Indifference Rule in Variable-Delay and Double-Reward Choice Procedures with Humans." Journal of the Experimental Analysis of Behavior. DOI:



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