Spear D J, Katz J L
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
J Exp Anal Behav. 1991 Sep;56(2):261-75. doi: 10.1901/jeab.1991.56-261.
Reinforcer magnitude and fixed-ratio requirement were varied under two second-order schedules. Under one, the first sequence of a fixed number of responses completed after the lapse of a 10-min fixed interval produced reinforcement. Under the second, a second-order progressive-ratio schedule, the fixed number of responses increased after each reinforcement. Either cocaine (0 to 300 micrograms/kg/inj) or food (0 to 5,700 mg/delivery) reinforcers were delivered. Under some conditions, a 2-s illumination of stimulus lights occurred on completion of each ratio sequence. Under the second-order schedule, as cocaine dose or amount of food increased, rates of responding increased; at the highest values, rates of responding decreased. Increases in the ratio requirement from 10 to 170 responses minimally decreased overall response rates. Under the second-order progressive-ratio schedule, increases in dose of cocaine or amount of food increased rates of responding; at the highest amounts of food, rates of responding decreased but response rates at the highest dose of cocaine remained relatively high. The highest ratio requirement that was completed (breaking point) depended on the dose of cocaine but was less dependent on the amount of food. Removing brief-stimulus presentations had a greater effect on completion of ratio requirements with cocaine compared to food.
在两种二阶强化程序下改变强化物强度和固定比率要求。在一种程序下，经过10分钟固定间隔后完成的固定次数反应的第一个序列会产生强化。在第二种程序，即二阶累进比率程序下，每次强化后固定反应次数会增加。给予可卡因（0至300微克/千克/注射）或食物（0至5700毫克/递送）作为强化物。在某些条件下，每个比率序列完成时会有2秒的刺激光照明。在二阶强化程序下，随着可卡因剂量或食物量增加，反应率增加；在最高值时，反应率下降。比率要求从10次反应增加到170次反应对总体反应率的降低极小。在二阶累进比率程序下，可卡因剂量或食物量增加会提高反应率；在食物量最高时，反应率下降，但在可卡因最高剂量时反应率仍相对较高。完成的最高比率要求（突破点）取决于可卡因剂量，但对食物量的依赖性较小。与食物相比，去除短暂刺激呈现对可卡因比率要求完成情况的影响更大。
