Doctoral Dissertation Research: Prosodic Encoding of Informativity

韵律在人类交际中起着至关重要的作用。单词的“旋律”可以传达单词本身无法传达的信息。例如，“你做了什么？”，可以表达友好的好奇或尖锐的反对，以及其他态度，这取决于说话者使用的韵律。能够使用和理解韵律线索是社会互动的基础，韵律是新生儿学习母语的第一件事。考虑到韵律对我们来说是多么自然，令人惊讶的是，我们还没有完全理解是什么影响了话语的韵律。据称起作用的一个因素是信息性。例如，“苹果”这个词在“小美人鱼吃了一个苹果”这样的句子中比“白雪公主吃了一个苹果”更有信息量，因为把苹果和小美人鱼联系在一起比把苹果和白雪公主联系在一起更出人意料。一般来说，一个单词信息量越大，它的韵律就越突出——信息量越大的单词可能比信息量较小的单词更长、更响亮。然而，要了解到底是什么促成了这个看似直观的概念，还需要进一步的研究。这项研究有可能为韵律发挥重要作用的其他领域提供信息——包括第一语言习得、第二语言理解、语言障碍和人际交往——并将加深我们对可以从韵律中提取哪些信息的理解。这种能力对于词汇量和语法有限的听众尤其重要，比如婴儿、第二语言学习者和失语症患者。本项目力求在韵律和信息性的不同研究传统之间建立联系。在之前的工作中，研究小组表明，韵律是由两种信息性之间的复杂相互作用形成的：(i)话语信息（例如，一个词是否第一次被提及）和（ii）统计因素（例如，一个词是经常使用的词还是不常用的词）。研究人员假设，这些结果实际上可以用一个统一的因素来解释，即实际发生的事情与说话者预期之间的差异程度——换句话说，说话者的惊讶程度。让我们再想想“白雪公主吃了一个苹果”。如上所述，“apple”这个词在这句话中的韵律突出程度应该相当低，因为它在上下文中是很容易预测的。然而，想象一下，说话者说这句话是为了回答别人问的“白雪公主吃了什么水果？”在这种情况下，“apple”这个词的发音可能会更有韵律，因为说话者可能会对谈话对象对一个著名童话故事的无知感到惊讶。基于这个想法，我们将进行一系列实验来进一步测试说话者的“惊讶”对他/她的韵律的影响程度。特别是，实验将调查说话者是否考虑到他们的对话伙伴的观点，说话者是否适应他们的合作伙伴的特点和不断变化的知识，以及非语言信息是否起作用。这些研究将揭示一些仍然存在争议的问题，比如人类的换位思考能力、我们追踪别人知道什么和不知道什么的能力，以及语言和其他认知方面（如视觉）之间的关系。作为一个整体，这个项目旨在提高我们对韵律的理解，韵律是口语交流最基本的方面之一。

Prosody plays a vital role in human communication. The 'melody' of words can convey information that the words themselves do not convey. For instance, a question like 'what did you do?' can express friendly curiosity or sharp disapproval, among other attitudes, depending on the prosody used by the speaker. Being able to use and understand prosodic cues is fundamental to social interaction, and prosody is one of the first things that newborn babies learn about their mother tongue. Considering how naturally prosody comes to us, it is surprising that we do not yet fully understand what influences the prosody of an utterance. One factor that has been claimed to play a role is informativity. For example, the word 'apple' is more informative in a sentence like 'the Little Mermaid ate an apple' than 'Snow White ate an apple', because it is more unexpected to associate apples with the Little Mermaid than Snow White. Broadly speaking, it seems that the more informative a word is, the more prominent it is prosodically--a more informative word is likely to be longer and louder than a less informative word. However, to understand what actually contributes to this seemingly intuitive notion, further research is needed. This research has the potential to inform other fields where prosody plays an important role--including first language acquisition, second language comprehension, language impairments and interpersonal communication--and will deepen our understanding of what information can be extracted from prosody. This ability is particularly important for listeners with a limited vocabulary and grammar such as infants, second language learners, and people with aphasia. This project strives to make connections between different research traditions on prosody and informativity. In prior work, the research group showed that prosody is shaped by a complex interplay between two kinds of informativity: (i) discourse information (e.g. whether a word is being mentioned for the first time) and (ii) statistical factors (e.g. whether a word is a frequently used word or an infrequent word). The researchers hypothesize that these results can in fact be explained by a unifying factor, namely the degree of difference between what actually happened and what the speaker had expected--in other words, how surprised the speaker is. Let us consider 'Snow White ate an apple' again. As mentioned above, the word 'apple' in this sentence should have fairly low prosodic prominence because it is highly predictable in the context. However, imagine the speaker said this sentence in response to someone asking 'what fruit did Snow White eat?' In this case, the word 'apple' might be pronounced with more prosodic prominence, because the speaker might be surprised by the conversational partner's lack of knowledge about a famous fairytale. Building on this idea, a series of experiments will be conducted to further test the extent to which the speaker's 'surprisal' influences his/her prosody. In particular, the experiments will investigate whether speakers take their conversational partner's perspective into account, whether speakers adapt to their partner's characteristics and changing knowledge, and whether non-linguistic information plays a role. These studies will shed light on still-debated questions about humans' perspective-taking abilities, our ability to track what others know and don't know, as well as the relationship between language and other aspects of cognition, such as vision. As a whole, this project aims to improve our understanding of prosody, one of the most fundamental aspects of spoken communication.