Linguistic complexity is commonly defined as the variedness and elaborateness of language production (Ellis, 2003). The definition resembles the philosophical definition of complexity as a function of the number of a system’s constituent elements, the variety of these constituents, and the elaborateness of their inter- relations (Rescher, 1998). Accordingly, the measurement of linguistic complex- ity involves quantitatively measuring the number and nature of linguistic sub- components and the interconnections between them (Bult ́e and Housen, 2014). The most commonly analyzed linguistic sub-components are syntax, lexicon, and—in synthetic languages—morphology. Syntactic complexity targets pri- marily phrasal, clausal, or sentential elements and is measured with indices such as dependent clauses per clause, complex phrases per phrase, or mean sentence length and so on (Kyle, 2016; Wolfe-Quintero et al., 1998).
