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Participants (N = 28) chose between smaller, immediate and
larger, delayed hypothetical monetary amounts in a cost and a
reward condition. For both conditions, the choice procedure
yielded equivalence points that measure the immediate amount
reward or cost that is subjectively equivalent to the larger delayed
reward or cost. Equivalence pOints from each of eight delays were
used to estimate a discounting parameter for both hyperbolic and
exponential discount functions. Hyperbolic functions accounted for
more of the variance in both the reward and the cost condition, and
delayed reward and cost discounting was significantly correlated.
Participants discounted the value of delayed rewards to a greater
degree than delayed costs. Previous research has found that
substance abusers discount delayed rewards more than controls.
Implications of the present find ings for substance abuse and other
health behaviors are discussed.