1. Literature review 1.1. Lexical diversity Lexical diversity (LD) has been defined as ‘the range of vocabulary and avoidance of repetition’ (Malvern et al., 2004). LD is still perceived as an indicator of second language (L2) writers’ writing abilities (Engber, 1995; Vo, 2019). As the illustrative indices to assess LD, the measure of textual lexical diversity (MTLD) and vocd-D are often utilised in many research studies. While MTLD is examined ‘as the mean length of sequential word strings in a text that maintains a given [type-token ratio] value’ (McCarthy & Jarvis, 2010, p. 384), vocd-D is calculated based on a series of randomly selected vocabulary. As LD can be examined in various ways and from various perspectives, researchers need to utilise multiple benchmarks, including MTLD and vocd-D, rather than a single yardstick (McCarthy & Jarvis, 2010).

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美国应用语言学协会 2021 年会议的精选海报展示

1. 文献综述 1.1. 词汇多样性 词汇多样性（LD）被定义为“词汇范围和避免重复”（Malvern et al., 2004）。LD 仍被视为第二语言 (L2) 作家写作能力的指标（Engber，1995；Vo，2019）。作为评估 LD 的说明性指标，文本词汇多样性 (MTLD) 和 vocd-D 的测量经常在许多研究中使用。虽然 MTLD 被检查为“保持给定 [type-token ratio] 值的文本中连续词串的平均长度”（McCarthy & Jarvis, 2010, p. 384），但 vocd-D 是基于一系列随机选择的词汇。由于 LD 可以通过多种方式和不同的角度进行检查，研究人员需要利用多个基准，包括 MTLD 和 vocd-D，而不是单一的标准（McCarthy &