|Budget Amount *help
¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1995 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1994 : ¥700,000 (Direct Cost : ¥700,000)
The present study investigated humans'and animals'choices in self-control and risky choice situations, in which reinforcer amounts and reinforcer delays or reinforcement probability were varied separately or together, to see whether a functional equivalence of reinforcer delay and probability can hold in a choice situation.
The present results with human subjects showed that in a self-control choice situation, humans were more sensitive to reinforcer amount than to delay, and their choices were, in a qualitative sense, described by the overall density of reinforcement rather than the local density of reinforcement as represented by the generalized matching law. Further, the results with rats as subjects showed that in a risky choice situation, rats preferred a variable food over a constant food when the energy budget condition (defined by their body weights) was negative, whereas they preferred the constant food over the variable food when it was positive ; that is, they showed "risk aversion" or "risk proneness" depending on their body weights. In another risky choice situation, it was found that rats were indifferent between certain, more delayd and uncertain, less delayd reinforcers. This finding clearly indicate that a functional equivalence of reinforcer delay and probability can hold in the present choice situation. Pigeons'choices were examined in situations where reinforcer amount and probability were varied separately or together. As a result, their choices were, in a qualitative sense, consisitent with predictions from the generalized matching law.
Taken together, it seems that probability can be transformed to delay intervals, thereby a risky choice situation may be reduced to the situation where reinforcer amount and delay are varied as in a self-control choice situation.