Adaptive Learning and Forgetting in an Unconventional Experimental Routine

Learning and forgetting were assessed concurrently in two experiments that involved the same unconventional routine. The schedule of reinforcement changed every session. Sessions were run back-to-back with a 23-hour mid-session break such that in a single visit to the testing chamber, the subject completed the second half of one session and the first half of the next. The beginning of a new session was either signaled or unsignaled. Experiment 1 involved concurrent variable interval-variable interval schedules with four possible reinforcer ratios. Response allocation was sensitive to the richer schedule and was retained through the mid-session break. Experiment 2 involved peak-interval schedules of varying durations. Temporal discrimination was rapidly acquired before and after the mid-session break, but not retained. Signaling the session change decreased control by past contingencies in both experiments, demonstrating that learning and forgetting can be investigated separately. Forgetting is often thought of as the inability to remember, but remembering and forgetting allow behavior to adapt to a changing environment in distinct and separable ways. These results suggest that the temporal structure of information can impact animals’ capacity to forget and remember.

两项采用同一非常规实验范式的实验同步评估了学习与遗忘过程。实验中，每一个实验单元的强化程式（reinforcement schedule）均会发生变更。实验单元以连续衔接的方式开展，中间设置23小时的中途休息时段；因此在单次进入测试箱的过程中，被试需完成当前实验单元的后半段，以及下一个实验单元的前半段。新实验单元的起始存在信号提示与无信号提示两种条件。实验1采用并发可变间隔-可变间隔强化程式，包含四种可设置的强化物比例。实验结果显示，反应分配对更优的强化程式具有敏感性，且该敏感性可通过实验中途休息得以保留。实验2采用不同时长的峰值间隔（peak-interval）强化程式。时间辨别能力可在实验中途休息前后快速习得，但无法通过休息得以保留。在两项实验中，对实验单元变更的信号提示均降低了过往强化偶联对行为的控制作用，这表明学习与遗忘过程可被独立研究。尽管遗忘常被定义为无法回忆，但记忆与遗忘实则以截然不同且可分离的方式助力行为适应动态变化的环境。本研究结果表明，信息的时间结构可影响动物的记忆与遗忘能力。