Intervention effects in clefts: a study in quantitative computational syntax

Clefts structures show an important asymmetry in interpretation: subject clefts can provide both corrective or new information foci, while non-subjects (objects, adjuncts) are only corrective. According to Belletti (2015), such an asymmetry arises from the fact that movement deriving subject clefts can target two focus positions, but non-subjects can target only one. In both cases a long-distance dependency is created, triggering locality effects. In this paper, we show that intervention effects causing ungrammaticality in certain configurations give rise to lower-than-expected frequencies in corresponding grammatical configurations. Based on sets of features that play a role in the syntactic computation of locality, we compare the theoretically expected and the actually observed counts of features in a corpus of thirteen syntactically annotated treebanks for three languages (English, French, Italian). We find the quantitative effects predicted by the theory of intervention locality. First, subject clefts, where no intervention is at play, are more frequent than object clefts, where intervention is at play. Secondly, object clefts are less frequent than expected in intervention configuration, while subject clefts are roughly as frequent as expected. Finally, we also find that the differential and direction of difference between expected and observed counts is directly proportional to the number of features that establish the intervention, the strength of the intervention. These results provide a three-fold contribution. First, they extend the empirical evidence in favour of the intervention theory of locality. Second, they provide theory-driven quantitative evidence, thus extending in a novel way the sources of evidence used to adjudicate theories. Finally, the paper provides a blueprint for future theory-driven quantitative investigations.