Growing up around different accents: the effect of speech variability on infant word recognition

父母的言语在婴儿的语言习得中起着至关重要的作用（Bruner，1983）。在许多家庭中，父母说话的口音不同。不同的口音（地区口音或外国口音）会引入语音变异性，即同一个单词会以两种不同的方式发音，这意味着婴儿接收到的输入是不一致的。先前的研究提出了相互矛盾的结果，这种不一致性对婴儿的语言学习的影响。婴儿早在五个月大时就能够区分熟悉和不熟悉的地区口音（Butler等人，2010年）。然而，这种对输入可变性的敏感性的影响尚不清楚。一方面，接触不同的口音可能有助于理解其他不熟悉的口音。这已经在一些基于实验室的研究中得到了证明，来自单一口音背景的儿童短暂地熟悉了一种外国口音，然后暴露于另一种不熟悉的口音。例如，来自美国英语语言背景的18个月大的孩子在接触澳大利亚英语，南美英语和印度英语后，更善于识别英国英语单词（Potter & Saffran，2017）。此外，短暂接触一个特定的不熟悉的口音有利于单词学习（Schmale等人，2012）和单词识别（Paquette-Smith等人，2020年，在这场战役中。在实验室之外，当从出生开始接触两种不同的口音时，Kartushina等人（2021）表明，在双口音家庭中长大的婴儿仍然更善于学习以不熟悉的口音出现的新单词。然而，关于熟悉的单词识别还没有得出任何结论。另一方面，暴露于两种不同的口音可能会延迟单词识别。例如，在家里暴露于加拿大口音和非母语英语口音的两岁奥尔兹在识别加拿大英语中的单词方面比来自单一口音背景的婴儿更差（Buckler等人，2017年）。从出生起暴露于两种口音的婴儿也比来自单一口音环境的婴儿对单词发音错误不那么敏感（Durrant等人，因此，在实验室中操纵口音暴露的研究与那些从出生开始观察多口音暴露的研究之间出现了关于单词识别的差异。这可能是由于长时间和短暂的多口音接触之间的真正差异，也可能是由于方法上的差异。迄今为止，关于这一主题的所有研究都是以行为措施为基础的。然而，有可能使用事件相关电位（ERP）数据来测量婴儿的单词识别（Korpilahti等人，2001年）。在现有的研究中加入ERP测量可以帮助调和任何可能因行为测量差异而产生的差异。本项目旨在通过结合行为和EEG测量，系统地研究多口音暴露对婴儿单词识别的影响。该研究将包括三个阶段，一个是检查来自单口音和多口音背景的婴儿的单词识别，下一个是在实验室中引入口音暴露的操作，最后一个是调查暴露于区域和外国口音变化是否会不同地调节婴儿的单词识别技能。这将允许在短时间和长时间暴露于一种以上口音的影响之间进行明确区分。

Parents' speech plays a crucial role in infants' language acquisition (Bruner, 1983). In many families, parents do not speak with the same accent. Different accents (regional or foreign) introduce speech variability, where the same word is pronounced in two different ways, meaning that the input received by the infant is inconsistent. Previous research presents conflicting findings as to the effect of this inconsistency on infants' language learning. Infants are able to distinguish familiar and unfamiliar regional accents as early as at five months of age (Butler et al., 2010). The effect of this sensitivity to input variability, however, is unclear. On one hand, exposure to different accents may facilitate understanding of other, unfamiliar accents. This has been shown in a number of lab-based studies where children from mono-accent backgrounds are briefly familiarised with a foreign accent, and then exposed to yet another unfamiliar accent. For example, 18-months-olds from an American English language background were better at recognising British English words after they had been exposed to Australian, Southern American and Indian English (Potter & Saffran, 2017). Moreover, brief exposure to a particular unfamiliar accent facilitates both word learning (Schmale et al., 2012) and word recognition (Paquette-Smith et al., 2020) in this accent. Outside of the laboratory, when the exposure to two distinct accents happens from birth, Kartushina et al. (2021) showed that infants raised in bi-accent households are still better at learning novel words presented in unfamiliar accents. No conclusion, however, has been reached about familiar word recognition. On the other hand, exposure to two different accents may delay word recognition. For example, two-year-olds exposed to both Canadian and a non-native English accent at home are worse at recognising words in Canadian English than infants from mono-accent backgrounds (Buckler et al., 2017). Infants exposed to two accents from birth are also less sensitive to word mispronunciations than infants from mono-accent environments (Durrant et al., 2015).A discrepancy, therefore, emerges between studies manipulating accent exposure in the laboratory and those looking at multi-accent exposure from birth, regarding word recognition. This could either be due to a genuine difference between prolonged and brief multi-accent exposure or due to methodological differences. All research on the topic to date has been based on behavioural measures. It is possible, however, to measure word recognition in infants using event-related potentials (ERP) data (Korpilahti et al., 2001). Adding ERP measures to the existing body of research could help reconcile any discrepancies that may arise from the differences in behavioural measures.This project aims to systematically examine the effect of multi-accent exposure on infant word recognition by using a combination of behavioural and EEG measures. The study will consist of three phases, one examining word recognition in infants from mono- and multi-accent backgrounds, the next one introducing a manipulation of accent exposure in the laboratory, and the final one investigating whether exposure to regional and foreign accents variations modulate differently infants' word recognition skills. This will allow for a clear distinction between the effects of brief and prolonged exposure to more than one accent.