The role of working memory in the cultural evolution of linguistic structure

人类语言赋予其使用者以无尽的新颖方式联合收割机和重新联合收割机组合信号的能力，以表达以前从未表达过甚至从未想过的意义。一个显而易见的问题是，我们的交流系统是如何进化成动物王国中独一无二的复杂系统的。但是，虽然语言是人类的一个决定性特征，但它的起源无法直接研究：它没有留下化石，也没有其他物种的自然发生的代理。近年来，研究人员已经找到了用人类参与者和计算机模型模拟语言进化的方法。一种使用迭代学习的实验范式已经出现，“一个个体通过观察另一个以同样方式获得行为的个体的类似行为来获得行为的过程”（Kirby等人，2008）。这项工作发现，人类有认知偏见，这意味着当一种新的语言需要后代能够学习并能够表达尽可能多的意义时，结构不可避免地出现。语言本身的外部机制可以解释为什么这种结构-我们通常称之为“语法”-在所有人类语言中进化。其中一种机制是工作记忆，它是一块“黑板”，它存储信息的时间足够长，以便在有意识的注意力中处理。工作记忆在耗尽和信息衰减之前只能处理有限数量的信息，任何试图记住一组在酒吧等待服务的饮料的人都可以证实这一点。这个项目将测试工作记忆的局限性是否会对语言施加压力，使其在文化演变过程中变得更加结构化。我不是第一个假设工作记忆可能构成了复杂语法出现的选择压力的人。特别是，柯立芝（2012）提出，随着语言的发展，语法结构被选为绕过工作记忆容量限制的一种手段。但是，尽管这一理论在直觉上很吸引人，但它从未通过实验证据得到证实。以前的工作也留下了模糊不清，这种“选择”是否是一种生物适应的语法，或文化进化的过程中，记忆施加了一个传输瓶颈，促进结构通过迭代学习。因此，本项目的重点是使用上述实验范式来测试当工作记忆的负荷更大时，语言结构是否通过文化传播更快地进化-或者在成功地传达信息方面提供更多的优势。深入了解推动语言进化的因素对于我们理解是什么使我们成为人类至关重要。要真正理解语言的起源，仅仅知道它是如何按时间顺序进化的是不够的。一个更根本的问题是，为什么它会沿着沿着这样的路线进化？换句话说，一旦这种新的交流系统的最早阶段开始运作，人类环境中的什么压力选择了这种交流系统的特定特征，或者使特定特征适应了？本项目旨在推进这一调查路线。如果更大的结构被证明对工作记忆的负荷更低，那么对于特定的后天记忆缺陷的治疗也有潜在的意义。关于语言结构是特定领域的还是更普遍的认知能力的指示，存在着相互矛盾的观点，但至少这些发现可以用于言语和语言治疗。

Human language gives its users the ability to combine and recombine signals in endlessly novel ways, to express meanings that have never been expressed or even thought of before. An obvious question is how our communication system evolved to be so uniquely complex in the animal kingdom. But while language is a defining human trait, its origins cannot be studied directly: it leaves behind no fossils, and there are no naturally-occurring proxies in other species. In recent years, researchers have found ways to simulate language evolution with human participants and computer models. An experimental paradigm has emerged which uses iterated learning, "a process in which an individual acquires a behaviour by observing a similar behaviour in another individual who acquired it in the same way" (Kirby et al. 2008). This work has found that humans have cognitive biases which mean that structure inevitably emerges when a new language needs to be both learnable by future generations and capable of expressing as much meaning as possible. Mechanisms external to language itself may explain why this structure - which we typically call 'grammar' - evolved in all human languages. One such mechanism is working memory, the 'blackboard' which stores information for just long enough to process it in conscious attention. Working memory can only handle a limited amount of information before it is exhausted and the information decays, as anyone who has tried to remember a group's drinks order while waiting to be served at a bar can confirm. This project will test whether the limitations of working memory could have put pressure on language to become more structured as it evolved culturally. I am not the first to hypothesise that working memory could have constituted a selective pressure for the emergence of complex grammar. In particular, Coolidge (2012) proposed that as language evolves, grammatical structure is selected for as a means of bypassing the limits of working memory capacity. But as intuitively appealing as this theory is, it has never been substantiated through experimental evidence. Previous work has also left vague whether this 'selection' is for a biological adaptation for syntax, or a process of cultural evolution whereby memory imposes a transmission bottleneck that promotes structure through iterated learning. The focus of this project is therefore to use the experimental paradigm outlined above to test whether linguistic structure evolves more quickly through cultural transmission - or provides more of an advantage in successfully communicating information - when the load on working memory is greater. Getting to the bottom of the factors that drive language evolution is central to our understanding of what makes us human. And to truly understand the origins of language, it is not enough simply to know how it evolved chronologically. A more fundamental question is why it evolved along the lines that it did; in other words, once the earliest stages of this new communication system got off the ground, what pressures in hominins' environment selected for particular characteristics of that communication system or made particular characteristics adaptive? This project seeks to advance that line of enquiry. There are also potential implications for the treatment of specific acquired memory deficits if greater structure is shown to place a lower load on working memory. There are conflicting views over whether linguistic structure is domain-specific or indicative of more general cognitive abilities, but at the least the findings could be of use to speech and language therapy.