Chapter 2. On the strength of morphological paradigms
This paper will present a historical explanation of radical pro-drop based on the strength of morphological paradigms. It will start out from the observation that East and mainland Southeast Asian languages (EMSEA) with their reduced or absent morphology are radical pro-drop, while West African Niger-Congo languages with similarly reduced or absent morphology have obligatory subject and object arguments. The reason for this is that the ancestor languages of Niger-Congo had a morphological paradigm expressing the features of [person] and [number] on the verb, while the ancestor languages of EMSEA had not. It will be argued that the existence of morphological paradigms keeps the frequency of [person] and [number] features above the critical percentage of 20–30% for linguistic change (s-curve model, Wang & Cheng 1970) and thus blocks the change from non-pro-drop to radical pro-drop in the West African languages concerned by passing on the frequency of the former morphological features to syntax and obligatory pronouns. In EMSEA languages, there is no morphological paradigm that pushes the frequency of these features up to the percentage that would be necessary for a change to non-pro-drop.