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.本研究通过两项采用同一非常规实验范式的实验，同步评估学习与遗忘过程。每轮实验的强化程式（reinforcement schedule）均会发生变更。实验回合（session）连续开展，中间设置23小时的中途休息时段，因此被试单次进入测试箱即可完成一轮实验的后半段与下一轮实验的前半段。新实验回合的起始分为提示与无提示两种条件。 实验1采用了四种不同强化物比例的并发可变间隔-可变间隔（variable interval, VI）强化程式。结果显示，反应分配对强化物更丰富的程式具有敏感性，且该敏感性可在中途休息时段后得以保留。 实验2采用了不同时长的峰值间隔（peak-interval）强化程式。时序辨别能力可在中途休息时段前后快速习得，但无法得以保留。 两项实验均表明，对实验回合变更进行提示可降低过往相倚程序（contingencies）对行为的调控作用，这证明学习与遗忘可被分别独立研究。尽管人们通常将遗忘视作无法回忆的状态，但回忆与遗忘实则以不同且可分离的方式，帮助行为适应不断变化的环境。本研究结果表明，信息的时序结构可影响动物的遗忘与回忆能力。