Seemingly similar: Subjects and displacement in grammar, processing, and acquisition

One of the core features of language is that words in a sentence often fulfill a dual task. For instance, in sentences with raising verbs like seem, what appears on the surface as the subject of seem, is interpreted as the subject of the embedded proposition. That is, in the sentence Tommy seems to have eaten the chocolate cake, Tommy appears as the subject of seem, but he’s not interpreted as the ‘seemer’. What is evaluated by seem is his property of being the eater of the cake. There is thus a discontinuity between the surface position and the position of interpretation; the subject has been displaced. In this thesis I investigate why subject displacement is difficult for our brain to process, and why it can go together with delays in language acquisition. Interestingly, raising verbs like seem not only display subject displacement, but also allow us to talk about realities that differ from our current one; they have an evidential meaning. As such, not only subject displacement can cause trouble in acquisition, but also the precise interpretational effects these raising verbs have. Another structure that displays subject displacement is the unaccusative structure (e.g. Tommy fell). The subject of unaccusative verbs has properties typically associated with syntactic objects, although it appears in subject position. Unaccusative verbs differ in this from unergative verbs for which the subject displays subject properties. Processing and acquisition of raising verbs is compared to processing and acquisition of unaccusative verbs to tear apart the separate effects of subject displacement and the specific interpretational requirements of raising verbs. In an innovative visual world experiment, we show that unaccusative structures with subject displacement delay interpretation compared to unergative structures. There is thus a close match between grammatical computation and processing. Furthermore, children from the age of five already distinguish between unaccusatives and unergatives. Apparently, children from that age are already aware of the subject displacement in unaccusative verbs. Raising verbs on the other hand, are acquired at a later point in acquisition. Moreover, depending on the precise interpretational effects, differences in the timing of acquisition occur. Similarly, different raising verbs have a different effect on processing in adults. This thesis has therefore shown that in order to understand the behavior of raising verbs in acquisition and processing, we have to distinguish on the one hand the effect they have in their capacity of raising verbs and in addition the effect in terms of their specific contribution to semantic interpretation. Their contribution to semantic interpretation affects processing and the course of acquisition. The precise interpretational effects do not come for free. It is therefore not only the syntactic computation, but also the computations required to establish the right semantics that influence the acquisition path. The language-acquiring child who has acquired subject displacement, does not necessarily possess all the tools that are required for an adult-like interpretation of the raising verbs. Linking the specific interpretation in terms of the reality under discussion to the particular raising verb takes somewhat longer.