Lawrence A B, Terlouw E M
Genetics and Behavioral Sciences Department, Scottish Agricultural College, Edinburgh, U.K.
J Anim Sci. 1993 Oct;71(10):2815-25. doi: 10.2527/1993.71102815x.
Environmentally induced stereotypies, commonly observed in farm and zoo animals, are behaviors that are relatively invariant, that are regularly repeated, and that serve no obvious function. However, there is as yet no accepted means of discriminating between normal and abnormal behavior, and the assumption that stereotypies are abnormal may mask the fact that they arise in part through processes that "normally" control behavior. There is growing evidence that stereotypies in sows and broiler breeders are strongly related to feeding motivation. For example, sows only develop oral stereotypies if their feed intake is restricted, and operant conditioning experiments have shown commercial levels of feed restriction to give rise to high levels of feeding motivation. Stereotypies in animals whose feed intake is restricted largely occur in the postprandial period, and ingestion of food has specifically been shown to elicit stereotypies in sows. These observations suggest that positive feedback from feeding produces a short-term increase in feeding motivation that at the end of the meal is directed toward available, alternative stimuli such as chains, the choice of stimuli reflecting the sensory feedback from the activity. Drinking behavior may also become an expression of feeding behavior after metabolic water requirements are met. In addition to these processes specific to feeding motivation, it seems likely that nonspecific processes, which operate more generally across motivational systems, contribute to the persistence of the behavior. Behavioral arousal may facilitate performance of active behaviors, and sensitization of the underlying neural elements may lead to the behavior being more easily elicited and maintained. A crucial factor in the sensitization process would seem to be the channeling of complex behavior by the environment into a few and very often repeated sequences of behavior. This approach suggests that stereotypies can be prevented by either reducing the level of motivation underlying the stereotypy, or by allowing for the expression of more complex behavior and thereby preventing the processes of channeling and sensitization from occurring.
环境诱导的刻板行为常见于农场和动物园动物中，是相对固定不变、经常重复且无明显功能的行为。然而，目前尚无公认的区分正常行为和异常行为的方法，认为刻板行为是异常行为的假设可能掩盖了这样一个事实，即它们部分是通过“正常”控制行为的过程产生的。越来越多的证据表明，母猪和肉种鸡的刻板行为与采食动机密切相关。例如，只有在采食量受到限制时母猪才会出现口部刻板行为，操作性条件反射实验表明，商业水平的采食量限制会引发高水平的采食动机。采食量受限的动物的刻板行为主要发生在餐后，具体研究表明，采食会引发母猪的刻板行为。这些观察结果表明，采食产生的正反馈会使采食动机在短期内增加，在进食结束时，这种动机指向如链条等可用的替代刺激物，刺激物的选择反映了活动中的感觉反馈。在满足代谢需水量后，饮水行为也可能成为采食行为的一种表现。除了这些特定于采食动机的过程外，似乎在更广泛的动机系统中起作用的非特异性过程也有助于这种行为的持续存在。行为唤醒可能促进主动行为的表现，潜在神经元的敏感化可能导致行为更容易被引发和维持。敏感化过程中的一个关键因素似乎是环境将复杂行为引导为少数且经常重复的行为序列。这种方法表明，可以通过降低刻板行为背后的动机水平，或者通过允许更复杂行为的表达，从而防止引导和敏感化过程的发生，来预防刻板行为。
