Magic moments: New word learning in children

Memory representations of words are thought to undergo changes with consolidation: Episodic memories of novel words are transformed into lexical representations that interact with other words in the mental dictionary. Behavioral studies have shown that this lexical integration process is enhanced when there is more time for consolidation. Neuroimaging studies have further revealed that novel word representations are initially represented in a hippocampally-centered system, whereas left posterior middle temporal cortex activation increases with lexicalization. In this study, we measured behavioral and brain responses to newly-learned words in children. Two groups of Dutch children, aged between 8–10 and 14–16 years, were trained on 30 novel Japanese words depicting novel concepts. Children were tested on word-forms, word-meanings, and the novel words’ influence on existing word processing immediately after training, and again after a week. In line with the adult findings, hippocampal involvement decreased with time. Lexical integration, however, was not observed immediately or after a week, neither behaviorally nor neurally. It appears that time alone is not always sufficient for lexical integration to occur. We suggest that other factors (e.g., the novelty of the concepts and familiarity with the language the words are derived from) might also influence the integration process.

学界普遍认为，词汇的记忆表征会随记忆巩固（consolidation）过程发生改变：新异词汇的情景记忆（episodic memories）会被转化为可与心理词典（mental dictionary）中其他词汇产生交互的词汇表征（lexical representations）。行为研究表明，当记忆巩固的时长增加时，该词汇整合（lexical integration）过程会得到增强。神经影像学（neuroimaging）研究进一步揭示，新异词汇的表征最初会在以海马体（hippocampus）为核心的系统中存在，而左后中颞叶皮层（left posterior middle temporal cortex）的激活程度则会随词汇化（lexicalization）进程提升。本研究针对儿童群体，测量了其对新习得词汇（newly-learned words）的行为与脑响应（behavioral and brain responses）。研究招募了两组荷兰儿童，年龄分别为8~10岁与14~16岁，让他们学习30个指代全新概念的日语新异词汇。分别在训练结束即刻与一周后，对儿童开展三项测试：词汇形式识别（word-forms）、词汇意义理解（word-meanings），以及新异词汇对已有词汇加工（word processing）的影响。研究结果与成人研究发现一致：海马体的参与程度随时间推移而降低。但无论在即刻测试还是一周后测试中，均未观察到词汇整合现象，无论是行为层面还是神经层面。由此可见，仅靠时长并不总能促成词汇整合的发生。我们推测，其他因素（如概念的新颖程度，以及学习者对词汇来源语言的熟悉程度）或许也会对整合过程产生影响。