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Participants (N = 17) chose between smaller, immediate and
larger, delayed hypothetical money amounts in two laboratory
sessions separated by 1 week. The choice procedure yielded
equivalence points at which participants were indifferent between
the smaller, immediate and the larger, delayed reward for eight
different delays of the larger reward. These equivalence points
then were used to estimate temporal discounting parameters
according to three different discounting functions. A hyperbolic
discounting function accounted for more of the variance than an
exponential function, which replicated earlier research.
Correlations across sessions showed that the discounting
parameters were reliable, and that the equivalence points were
reliable for delays greater than 1 month.