Discounting of delayed food rewards in pigeons and rats: Is there a magnitude effect?
Discounting of delayed food rewards in pigeons and rats: Is there a magnitude effect?
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DOI：
10.1901/jeab.2004.81-39
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发表时间：
2004-01-01
影响因子：
2.7
通讯作者：
Estle, SJ
中科院分区：
文献类型：
--
作者：
Green, L;Myerson, J;Estle, SJ
时间折扣是指随着收到奖励的时间增加，奖励的当前主观价值减少。人类的研究结果表明，当选择涉及假设的金钱奖励时，一个类似双曲线的函数描述了贴现函数的形式。此外，据报道，量级效应中，较小的奖励金额比较大的奖励金额折扣更大。目前的研究通过对鸽子和老鼠的真实奖励，即食物颗粒，来检验这些发现的跨物种普遍性。与人类一样，他们使用了一个调整数量的程序来估计即时奖励的数量，判断其价值与延迟奖励的价值相等。不同数量的延迟食物奖励（鸽子从5到32粒不等，大鼠从5到20粒不等）在延迟1到32秒不等的时间内进行了研究。一个简单的双曲线，类似于描述人类假设的货币奖励折扣的双曲线数学函数，描述了鸽子和老鼠对食物奖励的折扣。这些结果推广了贴现数学模型的通用性。鸽子对延迟食物奖励的折扣率高于老鼠。然而，与人类不同的是，鸽子和老鼠都没有表现出可靠的幅度效应：折现率并没有作为延迟奖励数量的函数而系统地变化。
Temporal discounting refers to the decrease in the present, subjective value of a reward as the time to its receipt increases. Results from humans have shown that a hyperbola-like function describes the form of the discounting function when choices involve hypothetical monetary rewards. In addition, magnitude effects have been reported in which smaller reward amounts are discounted more steeply than larger amounts. The present research examines the cross-species generality of these findings using real rewards, namely food pellets, with both pigeons and rats. As with humans, an adjusting amount procedure was used to estimate the amount of immediate reward judged equal in value to a delayed reward. Different amounts of delayed food rewards (ranging from 5 to 32 pellets in pigeons and from 5 to 20 pellets in rats) were studied at delays,varying from I s to 32 s. A simple hyperbola, similar to the hyperbola-like mathematical function that describes the discounting of hypothetical monetary rewards in humans, described the discounting of food rewards in both pigeons and rats. These results extend the generality of the mathematical model of discounting. Rates of discounting delayed food rewards were higher for pigeons than for rats. Unlike humans, however, neither pigeons nor rats showed a reliable magnitude effect: Rate of discounting did not vary systematically as a function of the amount of the delayed reward.