Stereotypy and perseveration in captive European starlings: consequences for decision-making

重复和不变的行为，如北极熊在动物园围栏里踱步或老鼠在实验室笼子里绕圈，在圈养的动物中很常见。这些没有明显功能的神秘行为模式被统称为刻板印象，对它们的解释一直是一个备受争议的话题。它们在让动物应对不适当的人工环境方面有作用吗？还是它们是潜在精神疾病的行为症状？支持后一种假设的证据正在开始积累。在将圈养动物的刻板印象与患有精神分裂症等精神疾病的人类的类似行为模式联系起来方面，笼养鸟类的实验发挥了重要作用。在一个被称为赌博任务的电脑游戏中，鸟类和人类都表现出非常相似的行为，在这个游戏中，它们必须从两个按钮中选择哪个按钮会提供奖励。与非刻板印象者相比，刻板印象者倾向于反复做出同样的选择，这种现象被称为“坚持不懈”。刻板印象和坚持都可能是负责行为模式排序的大脑系统功能障碍的症状。具体来说，人们认为，有这些症状的人类和动物已经破坏了参与停止当前反应并允许生物体切换到不同反应的途径。这一假设对广泛使用实验动物作为正常人类行为模型产生了令人担忧的影响。在实验动物身上进行的许多标准行为任务都可能受到毅力的影响，然而，在这一点上，我们几乎不知道这个问题可能有多大。因此，我们研究的目的是探索刻板印象行为和一些用于评估正常适应性行为的标准行为任务的表现之间的联系。我们选择研究圈养的欧洲椋鸟有两个原因：第一，因为笼子刻板印象和毅力之间联系的现有证据主要来自鸟类，第二，因为野生捕获的鸟类对实验室中适应行为的研究很重要。因此，特别重要的是要知道，当他们形成刻板印象时，他们的行为可能会发生多大程度的改变。我们将通过使用发育历史和当前的笼化操作，创造出不同程度的刻板印象的鸟类群体。从野外捕获的成年鸟和关在大笼子里的鸟应该显示出最低水平的刻板印象，而雏鸟从巢穴中取出，人工饲养，然后关在小笼子里的鸟应该显示出最高水平的刻板印象。我们将通过分析鸟类行为的录像带来衡量刻板印象，既可以用手，也可以用电脑软件自动跟踪鸟在笼子里的位置，并寻找它们的行为模式。此外，我们将在一些计算机控制的任务中测试鸟类：一个类似于上面提到的赌博任务，一个计时任务，以及一个测试风险敏感性的任务。我们选择后两项任务是因为它们通常用于行为研究。最后，我们将寻找单个鸟类展示的刻板印象程度与其在任务中的行为之间的联系。我们的研究将提供第一个数据，探索实验室动物的刻板行为如何影响一系列常见任务的正常行为。这些数据将使我们能够评估研究具有刻板印象的动物的潜在科学成本。如果这些成本是显著的，我们的研究结果将为进一步改善实验动物的笼子环境，以防止它们形成刻板印象提供强有力的支持。

Repetitive and unvarying behaviour, such as the pacing of a polar bear in a zoo enclosure or the circling of a mouse in a laboratory cage, is common in captive animals. These mysterious behaviour patterns with no obvious function are collectively known as stereotypies, and their explanation has been a topic of much debate. Do they have a function in allowing animals to cope with their inadequate artificial environments, or are they behavioural symptoms of underlying psychiatric disease? Evidence supporting the latter hypothesis is beginning to accumulate. Experiments with caged birds have played an important role in linking stereotypies in captive animals with similar behaviour patterns in humans with psychiatric illness such as schizophrenia. Stereotyping birds and humans both show very similar behaviour on a computer game, known as the gambling task, in which they have to choose which of two buttons will provide reward. In comparison to non-stereotyping individuals, stereotypers show a tendency to repeatedly make the same choice, a phenomenon known as perseveration. Both stereotypy and perseveration are likely to be symptoms of dysfunction in the brain systems responsible for the sequencing of behaviour patterns. Specifically, it is believed that humans and animals with these symptoms have damage to the pathways involved in stopping the current response and allowing the organism to switch to a different one. This hypothesis has worrying implications for the widespread use of laboratory animals as models of normal human behaviour. Many of the standard behavioural tasks performed on laboratory animals are likely to be affected by perseveration, however, at this point we have very little idea how big this problem is likely to be. The aim of our research is therefore to explore the links between stereotypic behaviour and performance on some standard behavioural tasks used to assess normal, adaptive behaviour. We have chosen to study captive European starlings for two reasons: first because the existing evidence for a link between cage stereotypies and perseveration comes mainly from birds, and second because wild-caught birds are important for the study of adaptive behaviour in the lab. It is therefore particularly important to know how much their behaviour might be altered when they develop stereotypies. We will create groups of birds differing in the degree of stereotypy they exhibit by using manipulations of both developmental history and current caging. Birds that are caught from the wild as adults and housed in large cages should show the lowest levels of stereotypy, whereas birds taken from their nests as chicks, hand raised and then housed in small cages should show the highest levels. We will measure stereotypies by analysing videotapes of the birds' behaviour, both by hand, and by using computer software that automatically tracks the position of a bird in a cage and looks for patterns in its behaviour. In addition, we will test birds on a number of computer-controlled tasks: a gambling task similar the one mentioned above, a timing task, and a task that tests sensitivity to risk. We have chosen these latter two tasks because they are commonly used in studies of behaviour. Finally, we will look for links between the degree of stereotypy an individual bird exhibits and its behaviour on the tasks. Our study will provide the first data exploring how stereotypic behaviour in laboratory animals affects normal behaviour on a range of common tasks. These data will allow us to assess the potential scientific costs of studying animals with stereotypies. If these costs are significant, our findings will provide strong support for further improving the cage environments of laboratory animals in order to prevent them from developing stereotypies.