Morphological complexity in written L2 texts

Morphological complexity (MC) is a relatively new construct in second language acquisition
(SLA). After critically discussing existing approaches to calculating MC in first- and second-
language acquisition research, this article presents a new operationalization of the construct,
the Morphological Complexity Index (MCI). The MCI is applied in two case studies based
on argumentative written texts produced by native and non-native speakers of Italian and
English. Study 1 shows that morphological complexity varies between native and non-native
speakers of Italian, and that it is significantly lower in learners with lower proficiency levels.
The MCI is strongly correlated to proficiency, measured with a C-test, and also shows
significant correlations with other measures of linguistic complexity, such as lexical diversity
and sentence length. Quite a different picture emerges from Study 2, on advanced English
learners. Here, morphological complexity remains constant across natives and non-natives, and
is not significantly correlated to other text complexity measures. These results point to the fact
that morphological complexity in texts is a function of speakers’ proficiency and the specific
language under investigation; for some linguistic systems with a relatively simple inflectional
morphology, such as English, learners will soon reach a threshold level after which inflectional
diversity remains constant.