Word learning in early, middle and late adulthood

在认知衰老领域，众所周知，一些认知功能在一生中保持相对稳定(例如，长时表征、自动加工、内隐学习)，而另一些则逐渐衰退(例如，执行控制、记忆维持/提取和速度)。语言使用也呈现出混合的老化轨迹：语音、词汇、语义和句法知识相对保留，而获取这些知识的难易程度和对其激活的控制随着年龄的增长而下降。这种分离如何影响一生中词汇学习的动力和效率尚不清楚。本研究计划的目的是调查婴幼儿和儿童时期词汇习得文献中记录的几种关键词汇学习机制与年龄相关的稳定性和衰退性，并建立补偿性权衡(例如，对储存知识的依赖)可以在多大程度上延缓涉及更大程度的执行控制和外显计算的学习机制的衰退。更好地了解支持单词学习的机制是如何随着寿命的变化而变化的，对老年人的生活质量具有重要影响。事实上，由于今天预期寿命的增加，以及预期这些增加的许多年将在相对健康的情况下度过，老年人获得新知识、新技能或学习新语言的机会已经很多。目标群体将是年轻人(25岁)、中年人(40岁至50岁)和老年人(65岁)。中年群体是至关重要的，因为它不仅使我们能够绘制出更准确的单词学习机制的轨迹，而且还可以确定基于上下文和长期表征的补偿是否比传统假设更早开始起作用。正在研究的学习机制将是：(1)相邻依赖：这代表了一种基于隐含地计算语音输入中的统计规则的域通用学习形式。我们预计，随着时间的推移，这种类型的学习将相对稳健。(2)非相邻依存性：这将实例化一种既依赖联想又依赖抽象的单词学习形式，这是一种更复杂的学习形式，可能会利用老年人缺乏的加工资源。(3)抽象模式：这些实验将把抽象模式的学习和概括实例化到全新的材料上，不同于相邻依赖关系和非相邻依赖关系，相邻依赖关系不需要对新材料进行概括，而非相邻依赖关系只需要对新材料进行部分概括。(4)基于规则的抽象(一阶逻辑)：这将与前面的一组实验类似，不同的是，定义语言可接受单词的抽象模式将由包含逻辑运算符(相当于IF、THEN、ELSE)的语法来规范。这是四套中最具语言特色的学习形式。它对衰老的适应能力在很大程度上是未知的。上面的学习机制将与它们匹配的外显学习机制进行比较。总体而言，这项研究将突出语言学习在一生中的动态化和可塑性，并将有助于我们从理论上理解语言加工、语言学习和认知老化。

In the field of cognitive aging, it is well established that some cognitive functions remain relatively stable over the lifespan (e.g., long-term representations, automatic processes, implicit learning) while others progressively decline (e.g., executive control, memory maintenance/retrieval, and speed). Language use shows a mixed aging trajectory as well: Phonological, lexical, semantic and syntactic knowledge is relatively preserved, whereas the ease of access to that knowledge and control over its activation tend to degrade with age. How this dissociation affects the dynamics and efficiency of word learning over the lifespan is unclear.The purpose of this research programme is to investigate the age-related stability vs. decline of several key word-learning mechanisms that have been documented in the word-acquisition literature in infancy and childhood, and to establish the extent to which compensatory trade-offs (e.g., reliance on stored knowledge) can stave off the decline of learning mechanisms that involve a greater degree of executive control and explicit computation. A better understanding of how the mechanisms underpinning word learning change over the lifespan has important consequences for older adults' quality of life. Indeed, owing to today's increased life expectancy and the expectation that many of those additional years will be spent in relatively good health, opportunities for older adults to acquire new knowledge, new skills, or learn new languages have flourished.The target groups will be young adults (< 25y), middle-age adults (40y to 50y), and older adults (> 65y). The middle-age group is critical because it will enable us not only to draw a more accurate trajectory of word learning mechanisms, but also to establish whether compensation based on context and long-term representations begins to operate earlier than traditionally assumed. The learning mechanisms under study will be: (1) Adjacent dependencies: This represents a form of domain-general learning based on implicitly computing statistical regularities in the speech input. We expect this type of learning to be comparatively robust over time. (2) Non-adjacent dependencies: This will instantiate a form of word learning that relies on both association and abstraction, a more complex form of learning that could potentially engage processing resources that are in short supply in older adults. (3) Abstract patterns: These experiments will instantiate abstract pattern learning and generalisation to entirely new materials, unlike adjacent dependencies which require no generalisation to new materials and non-adjacent dependencies which require only partial generalisation to new materials. (4) Rule-based abstraction (first-order logic): This will be similar to the previous set of experiments, except that the abstract patterns defining the acceptable words of the language will be regulated by a grammar containing logical operators (equivalent to if, then, else). This is the most language-specific form of learning of the four sets. Its resilience to aging is largely unknown.The above learning mechanisms will be compared to their matched explicit-learning counterpart. As a whole, this study will highlight the dynamics and plasticity of language learning over the lifespan and, in doing so, will contribute to our theoretical understanding of language processing, language learning, and cognitive aging.