Perspectives on morphological complexity

This paper discusses the notion of morphological complexity and differentiates language external complexity (E-complexity) from language internal complexity (I-complexity). While E-complexity is measurable on the basis of the statistical occurrences of affixes and their combinations with roots, I-complexity can be measured on the basis of the number of operations applying in the derivation of morphological forms. The author compares results from studies classifying languages based on their E-complexity to results from studies showing similarities between languages with respect to I-complexity. The comparison reveals that languages with different E-complexity may have similar I-complexity. The author revisits results from psycholinguistic and parsing experiments and discusses how the two sorts of complexity can be reduced. Finally, the role of I- and E-complexity for the understanding of the relation between the language faculty and the external systems is considered.