Doctoral Dissertation Research:Examining Inhibitory Control and Language Flexibility in Adult Second Language Learning: A Neurocognitive Investigation

在美国，数以百万计的成年人发现出于个人、商业和政府相关的目的学习第二语言是有益的，甚至是必要的。然而，第二语言学习是一项复杂和具有挑战性的努力，导致学习结果有很大的变异性。一些学习者达到了可接受的熟练程度，而另一些学习者则不能。尽管如此，解释成人第二语言学习成功程度不同的因素仍然没有完全被理解。研究人员努力解释在学习第二语言时谁会成功，其中一个方法是找出与成功的成人第二语言学习相关的一组个人因素。本论文研究了两个认知因素，这两个因素已被证明在双语学习中起作用，最近也被提出对第二语言学习有贡献。第一个因素，抑制性控制，被定义为个体故意抑制自动反应的能力，已被证明是双语语言控制的关键。第二个因素，语言灵活性，指的是个人对第一语言变化的容忍能力，这在双语语言处理中是明显的。本论文将考察这些因素在第二语言学习者掌握双语后所起的作用。要做到这一点，我们首先将评估处于学习西班牙语的早期、中期或后期阶段的成年西班牙语学习者的第二语言熟练程度。其次，将对学习者的抑制控制能力进行行为测量，基于大脑的电生理测量将通过检查他们发展的西班牙语对他们的第一语言处理能力的影响程度来评估语言灵活性。最后，对这些数据进行分析，以检验抑制性控制能力和语言灵活性在多大程度上预测学习者的熟练程度。这项研究的发现有望对理论和实践产生广泛的影响。这项研究将使我们从理论上理解导致学习第二语言这一复杂任务的潜在认知机制和大脑机制。这增加了对语言学习方式的理解，反过来将有助于第二语言教学的方法论方法。例如，教学材料可以设计成利用或支持个别学习者的特征，如他们的抑制控制能力。该项目还将在研究设计、认知和基于大脑的数据分析、电生理数据和数据解释等领域为研究生和本科生的研究助理提供宝贵的实践经验。最后，鉴于进行这项研究的机构有不同的学生群体，它将涉及在高等教育中往往代表不足的群体的学生，其中许多人本身就是第二语言学习者。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Within the United States, millions of adults find it beneficial or even necessary to learn a second language for personal, business, and government related purposes. Yet, second language learning is a complex and challenging endeavor that results in a great deal of variability in learning outcomes. Some learners reach acceptable levels of proficiency for their purposes whereas other learners do not. Nonetheless, the factors that explain the varying levels of success in adult second language learning are still not fully understood. One way in which researchers work to explain who is expected to be successful when learning a second language is to identify the set of individual factors that are associated with successful adult second language learning. This dissertation project investigates two cognitive factors that have been shown to play a role in bilingualism and that have also recently been proposed to contribute to second language learning. The first factor, inhibitory control, is defined as an individual's ability to deliberately suppress automatic responses and has been shown to be key for bilingual language control. The second factor, language flexibility, refers to an individual's ability to tolerate changes to their first language and is evident in bilingual language processing. The dissertation will examine the role of these factors in second language learners as they become bilingual. To do so, we will first assess second language proficiency with multiple measures in adult learners of Spanish who are at early, intermediate, or late stages of learning the language. Second, behavioral measures will be taken of learners' inhibitory control ability, and brain-based, electrophysiological measures will assess language flexibility by examining the extent to which their developing Spanish affects their first language processing. Finally, these sets of data will be analyzed to examine to what extent inhibitory control abilities and language flexibility predict the level of proficiency that the learners achieve. The findings from the study are expected to have broad implications for theory and practice. The research will inform our theoretical understanding of the underlying cognitive and brain mechanisms that contribute to the complex task of learning a second language. This increased understanding about how languages are learned, in turn, will inform methodological approaches for teaching second languages. For example, instructional materials can be designed that leverage or support individual learner characteristics such as their inhibitory control ability. This project will also provide invaluable hands-on experience to graduate and undergraduate research assistants in areas including research design, data analyses of cognitive and brain-based, electrophysiological data, and data interpretation. Finally, given that the institution where this research will take place has a diverse student population, it will involve students from groups who are often underrepresented in higher education, many of whom are second language learners themselves.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.