Although undesired under a theoretical viewpoint, natural languages often show cases of “true” optionality. According to a reformulation of the Interface Hypothesis (Sorace 2006), highly complex constructions are more susceptible to optionality and change. Psych verbs that select a subject dative experiencer fall under this definition. Ibero-Romance languages use different strategies to reduce this morphosyntactic inconsistency. Whereas Catalan and Spanish reinforce the deviant construction through additional morphological markers (dative clitic doubling and subsequent grammaticalization of the clitic as subject-verb agreement marker), Portuguese avoids inherent datives at all, using structural case instead. These innovations in argument structure have significant consequences: clitic doubling with full DPs and the grammaticalization of the clitic pronouns are blocked, in contrast to Catalan and Spanish. It becomes evident that a closer look at how argument structure is codified in the lexicon is needed in order to better understand processes of language change.
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