Background and aims

Previous research into word learning in children with developmental language disorder (DLD) indicates that the learning of word forms and meanings, rather than form-referent links, is problematic. This difficulty appears to arise with impaired encoding, while retention of word knowledge remains intact. Evidence also suggests that word learning skills may be related to verbal working memory. We aimed to substantiate these findings in the current study by exploring word learning over a series of days.

Methods

Fifty children with DLD (mean age 6; 11, 72% male) and 54 age-matched typically developing (TD) children (mean age 6; 10, 56% male) were taught eight novel words across a four-day word learning protocol. Day 1 measured encoding, Days 2 and 3 measured re-encoding, and Day 4 assessed retention. At each day, word learning success was evaluated using Naming, Recognition, Description, and Identification tasks.

Results

Children with DLD showed comparable performance to the TD group on the Identification task, indicating an intact ability to learn the form-referent links. In contrast, children with DLD performed significantly worse for Naming and Recognition (signifying an impaired ability to learn novel word forms), and for Description, indicating problems establishing new word meanings. These deficits for the DLD group were apparent at Days 1, 2, and 3 of testing, indicating impairments with initial encoding and re-encoding; however, the DLD and TD groups demonstrated a similar rate of learning. All children found the retention assessments at Day 4 difficult, and there were no significant group differences. Finally, verbal working memory emerged as a significant moderator of performance on the Naming and Recognition tasks, such that children with DLD and poor verbal working memory had the lowest levels of accuracy.

Conclusions

This study demonstrates that children with DLD struggle with learning novel word forms and meanings, but are unimpaired in their ability to establish new form-referent links. The findings suggest that the word learning deficit may be attributed to problems with encoding, rather than with retention, of new word knowledge; however, further exploration is required given the poor performance of both groups for retention testing. Furthermore, we found evidence that an impaired ability to learn word forms may only be apparent in children who have DLD and low levels of verbal working memory.

Implications

When working with children with DLD, speech-language pathologists should assess word learning using tasks that evaluate the ability to learn word forms, meanings, and form-referent links to develop a profile of individual word learning strengths and weaknesses. Clinicians should also assess verbal working memory to identify children at particular risk of word learning deficits. Future research should explore the notion of optimal intervention intensity for facilitating word learning in children with poor language and verbal working memory.

中文翻译：

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发育性语言障碍儿童的单词学习和言语工作记忆

背景和目标

先前对患有发育性语言障碍 (DLD) 儿童的单词学习的研究表明，单词形式和含义的学习，而不是形式指称链接，是有问题的。这种困难似乎随着编码受损而出现，而单词知识的保留保持不变。证据还表明，单词学习技能可能与语言工作记忆有关。我们的目的是通过在一系列的日子里探索单词学习来证实当前研究中的这些发现。

方法

50 名患有 DLD 的儿童（平均年龄 6 岁；11 名，72% 为男性）和 54 名年龄匹配的正常发育 (TD) 儿童（平均年龄 6 岁；10 名，56% 为男性）在为期四天的单词学习方案中学习了八个新单词. 第 1 天测量编码，第 2 天和第 3 天测量重新编码，第 4 天评估保留。每天，使用命名、识别、描述和识别任务评估单词学习成功与否。

结果

患有 DLD 的儿童在识别任务中表现出与 TD 组相当的表现，表明他们具有完整的学习形式参照链接的能力。相比之下，患有 DLD 的儿童在命名和识别（表示学习新词形式的能力受损）和描述方面表现明显更差, 表示建立新词义的问题。DLD 组的这些缺陷在测试的第 1、2 和 3 天很明显，表明初始编码和重新编码存在损伤；然而，DLD 和 TD 组表现出相似的学习率。所有孩子都发现第 4 天的保留评估很困难，并且没有显着的组别差异。最后，言语工作记忆成为命名和识别任务表现的重要调节因素，因此患有 DLD 和言语工作记忆差的儿童的准确性最低。

结论

这项研究表明，患有 DLD 的儿童在学习新的单词形式和含义方面遇到了困难，但他们建立新的形式指称联系的能力没有受到影响。研究结果表明，单词学习缺陷可能归因于编码问题，而不是新单词知识的保留问题；然而，鉴于两组在保留测试中的表现不佳，还需要进一步探索。此外，我们发现有证据表明，学习单词形式的能力受损可能只在患有 DLD 和低水平的语言工作记忆的儿童中表现出来。

启示

在与患有 DLD 的儿童一起工作时，语言病理学家应该使用评估学习单词形式、含义和形式指称链接的能力的任务来评估单词学习，以形成个人单词学习优势和劣势的概况。临床医生还应评估口头工作记忆，以确定有特定单词学习缺陷风险的儿童。未来的研究应该探索最佳干预强度的概念，以促进语言和言语工作记忆较差儿童的单词学习。