Morphological complexity and rated writing proficiency

Linguistic complexity measures are used to describe second language (L2) performance and assess levels of proficiency and development. Although morphology is considered crucial in L2 acquisition, morphological complexity has been relatively neglected, hindering comprehensive views of grammatical complexity in L2. This article presents an application of a recently proposed metric of morphological diversity, the Morphological Complexity Index (MCI), in an L2 Spanish corpus of 113 essays classified into four proficiency levels by expert evaluators. The aim of the study is to investigate the relationships of MCI with subjectively rated proficiency and with other four quantitative measures of L2 complexity. Results indicate that morphological complexity, as measured by MCI, does not vary significantly across proficiency levels in this corpus. The MCI shows significant correlations with lexical but not with syntactic complexity measures. Findings are interpreted in the light of the characteristics of the corpus and the acquisition of the Spanish verbal system.