... In addition to the number of formal errors in the texts and the use of syntactic and cohesive devices, these characteristics include text length, the complexity and sophistication of the words used in the text, and the variety of the words in the text. Of particular relevance to the present study, metrics related to the quantity, range, and variety of the vocabulary used in a text-that is, metrics related to the text's lexical richness-are important predictors of writing quality as judged by experts (e.g., Engber, 1995;Grobe, 1981;Jarvis, 2002;Jarvis, Grant, Bikowski, & Ferris, 2003;Malvern, Richards, Chipere, & Durán, 2004;McNamara, Crossley, & McCarthy, 2010;Nold & Freedman, 1977). 1 Yet, as Jarvis (2013a) points out, despite the proliferation of lexical richness metrics in quantitative linguistics, it is not clear how well these do indeed measure aspects of lexical richness. To elaborate, lexical richness metrics are generally evaluated on the basis of how sensitive they are to text length (e.g., McCarthy & Jarvis, 2007, 2013Treffers-Daller, 2013;Tweedie & Baayen, 1998) and how well they correlate with variables representing other constructs, such as essay quality, language proficiency or other writer and talker characteristics (e.g., Daller, van Hout, & Treffers-Daller, 2003;Treffers-Daller, 2013;Treffers-Daller, Parslow, & Williams, 2016). ...