Cramer C P, Pfister J P, Haig K A
Department of Psychology, Johns Hopkins University, Baltimore, Maryland.
Dev Psychobiol. 1988 Jan;21(1):1-24. doi: 10.1002/dev.420210102.
These experiments explore the role of preweaning experience in learning during the juvenile period. Pups that had been reared with many nipples available reached criterion on an 8-arm radial maze in a few trials; conversely, pups reared with only a few nipples required 3 times the number of trials to reach criterion (Experiment 1). Pups that had been reared with relatively few nipples available rarely nipple-shifted, while those that had been reared with a particularly high density of nipples shifted more frequently (Expt 2). A rearing procedure was devised that allowed precise experimental control of all phases of the suckling experience (Expt 3). Allowing or preventing a single behavior, nipple-shifting, while holding all other variables constant, was sufficient to affect acquisition of the maze task. In Experiment 4, the specificity of the early experience for later tasks was explored using a variety of nonspatial, lever-pressing operants. Rearing condition did not affect acquisition of a lever-pressing operant or of a visual discrimination task. However, pups reared with a high density of nipples responded at higher rates to a variable interval schedule and were more resistant to extinction. The possibility that strategy, rather than learning ability, was affected by rearing condition was assessed using a 2-arm maze task that was structured to present an optimal strategy of either win-shift or win-stay (Expt 5). The ease with which rats acquired the win-stay task was unaffected by rearing condition; all groups performed at about chance levels. However, pups reared with many nipples more readily acquired the win-shift task.
这些实验探究了断奶前经历在幼年期学习过程中的作用。在多个乳头可供使用的环境中饲养的幼崽，在八臂放射状迷宫实验中只需经过几次试验就能达到标准；相反，在只有少数乳头的环境中饲养的幼崽，达到标准所需的试验次数是前者的3倍（实验1）。在乳头相对较少的环境中饲养的幼崽很少出现乳头转移行为，而在乳头密度特别高的环境中饲养的幼崽乳头转移行为更频繁（实验2）。设计了一种饲养程序，以便能精确地对哺乳经历的各个阶段进行实验控制（实验3）。在保持所有其他变量不变的情况下，允许或阻止单一行为——乳头转移，就足以影响迷宫任务的习得。在实验4中，使用各种非空间的杠杆按压操作性条件反射来探究早期经历对后期任务的特异性。饲养条件不影响杠杆按压操作性条件反射或视觉辨别任务的习得。然而，在乳头密度高的环境中饲养的幼崽对可变间隔时间表的反应率更高，并且更不容易消退。使用双臂迷宫任务评估饲养条件影响的是策略而非学习能力的可能性，该任务被设计为呈现赢了就转换或赢了就停留的最佳策略（实验5）。大鼠习得赢了就停留任务的难易程度不受饲养条件的影响；所有组的表现都大致处于随机水平。然而，在有多个乳头的环境中饲养的幼崽更容易习得赢了就转换任务。
