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

人类语言赋予了使用者以无休止的新奇方式组合和重组信号的能力，以表达以前从未表达过或甚至从未想过的含义。一个明显的问题是，在动物界，我们的交流系统是如何进化成如此独特的复杂的。但是，虽然语言是人类的一个决定性特征，但它的起源不能直接研究：它没有留下任何化石，也没有在其他物种中自然产生的替代品。近年来，研究人员已经找到了用人类参与者和计算机模型来模拟语言进化的方法。出现了一种使用迭代学习的实验范式，“一个人通过观察以同样方式获得该行为的另一个人的类似行为来获得该行为的过程”(Kirby等人)。2008年)。这项研究发现，人类存在认知偏差，这意味着当一种新的语言既要能被后代学习，又要能尽可能多地表达意义时，这种结构不可避免地会出现。语言本身之外的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，这是一块存储信息的“黑板”，其存储时间恰好足以让人有意识地处理信息。工作记忆在耗尽之前只能处理有限的信息，这些信息会腐烂，任何在酒吧等待服务时试图记住一群人的饮品订单的人都可以确认这一点。这个项目将测试工作记忆的局限性是否会给语言带来压力，使其在文化演变过程中变得更加结构化。我并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性压力的人。特别是，柯立芝(2012)提出，随着语言的发展，语法结构被选择作为一种绕过工作记忆容量限制的手段。但是，尽管这一理论直观上很有吸引力，但它从未得到实验证据的证实。以前的研究也没有明确指出，这种“选择”是对句法的生物适应，还是文化进化的过程，在文化进化过程中，记忆会造成传递瓶颈，从而通过反复学习促进结构的形成。因此，本项目的重点是使用上面概述的实验范式来测试当工作记忆的负荷更大时，语言结构是通过文化传播更快地演变，还是在成功地交流信息时提供更多的优势。弄清推动语言进化的因素对于我们理解人类的本质是至关重要的。要真正理解语言的起源，仅仅知道它是如何按时间顺序演变的是不够的。一个更根本的问题是，为什么它会沿着它曾经的路线进化；换句话说，一旦这种新的通信系统的最早阶段开始，人类环境中的哪些压力选择了该通信系统的特定特征，或者使特定的特征具有适应性？该项目旨在推进这一调查路线。如果显示出更大的结构对工作记忆施加了较低的负荷，那么治疗特定的获得性记忆缺陷也有潜在的意义。关于语言结构是特定领域的，还是代表更一般的认知能力，存在着相互矛盾的观点，但至少这些发现可能对言语和语言治疗有用。

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.