Pitts R C, Malagodi E F
Department of Psychology, University of Florida, Gainesville 32611.
J Exp Anal Behav. 1991 Jul;56(1):21-32. doi: 10.1901/jeab.1991.56-21.
Lever pressing by 2 squirrel monkeys was maintained under fixed-interval 6-min and fixed-interval 2-min schedules of electric-shock presentation. Preference for these schedules was assessed during three experimental phases. In all phases, responses on one lever produced shock according to one or the other fixed-interval schedule, and responses on a second, changeover, lever switched between schedules. The opportunity to change over was presented during separate choice periods (during which the fixed-interval schedules did not operate) that followed the first through fourth shocks in each schedule. If no changeover occurred during those choice periods, a changeover automatically occurred following the fifth shock. In Phase I, durations of the choice periods were fixed. In Phase II, the choice periods equaled a proportion of their respective fixed interval. During Phase III (completed with 1 monkey) a response on the changeover lever during a given choice period reinstated the most recent fixed interval, and a failure to respond resulted in a changeover. During each of these phases, distinct preferences developed for the 6-min schedule. These results suggest that the maintenance of lever pressing by fixed-interval presentation of electric shock may not be an example of positive reinforcement, and that the response-maintaining characteristics of shock presentation may derive from other properties of the schedule.
两只松鼠猴的杠杆按压行为在电击呈现的固定间隔6分钟和固定间隔2分钟的时间表下得以维持。在三个实验阶段对这些时间表的偏好进行了评估。在所有阶段，对一个杠杆的反应会根据其中一个固定间隔时间表产生电击，而对第二个转换杠杆的反应则在不同时间表之间切换。在每个时间表的第一次到第四次电击之后的单独选择期（在此期间固定间隔时间表不运行）会提供转换的机会。如果在那些选择期内没有发生转换，那么在第五次电击之后会自动发生转换。在第一阶段，选择期的时长是固定的。在第二阶段，选择期等于其各自固定间隔的一定比例。在第三阶段（用1只猴子完成），在给定选择期内对转换杠杆的一次反应会恢复最近的固定间隔，而没有做出反应则会导致转换。在这些阶段中的每一个阶段，对6分钟时间表都形成了明显的偏好。这些结果表明，通过电击的固定间隔呈现来维持杠杆按压可能不是正强化的一个例子，并且电击呈现的反应维持特性可能源自时间表的其他属性。
