The Neuronal Reality of the Nominal Hierarchy: fMRI Observations on Animacy in Sentence Comprehension

Animacy makes a fundamental contribution to the categorization of everyday experiences. In this way, the differentiation between animate and inanimate entities is important for the identification of potentially more or less causative characters. With respect to the language system, animacy is a semantic feature of universal importance. Cross-linguistic research revealed a three-tiered animacy hierarchy: Human ] Animate ] Inanimate. This animacy hierarchy is reflected by different linguistic properties depending on the language under consideration. In some languages, animacy information has an influence on word order (e.g. German, Finnish), in others case marking is morphologically determined by this feature, and an effect of animacy on sentence interpretation can be observed (e.g. Fore, Hindi). The aim of the present thesis is to shed light on the impact of animacy on sentence processing in German. Although animacy is a purely semantic feature, an influence of this parameter on syntactic structure has been observed such that animate arguments should precede inanimate arguments within the German middle field (e.g. Gestern wurde dem Redakteur der Artikel präsentiert; yesterday was [the editor]A-OBJ [the article]I-SUBJ presented). Since German is a language with flexible word order, the order of the two arguments can also be changed, as demonstrated in the sentence Gestern wurde der Artikel dem Redakteur präsentiert; yesterday was [the article]I-SUBJ [the editor]A-OBJ presented. Although both sentences are grammatically correct, the linearization of arguments within the latter sentence is unexpected with respect to animacy. Nevertheless, this sentence reflects the preferred subject-before-object order which is violated in the first example. As the examples demonstrate, the animacy principle is one of several language-specific linearization principles whose influence on argument order cannot always be clearly differentiated. Besides the influence of animacy on the linearization of arguments, this feature is also interesting from a relational point of view. The most natural kind of a transitive sentence comprises an information flow from the causer of an event which is high in animacy to the argument that is lower in animacy and agency. Besides this unmarked transitive sentence structure, German also allows for an asymmetrical and therefore less natural distribution in which either both arguments are animate (Gestern hat der Redakteur den Mitarbeiter entdeckt, yesterday has [the editor]A-SUBJ [the colleague]A-OBJ discovered) or the assignment of animacy is even completely reversed (Gestern hat der Artikel den Redakteur überrascht, yesterday has [the article]I-SUBJ [the editor]A-OBJ surprised). However, such asymmetrical distributions are supposed to result in deviations from the unmarked transitive sentence structure indicating that the relation between sentential arguments at least partially depends on their animacy. Since previous behavioral and neurophysiological data provided evidence for an influence of animacy in syntactic processing the present work aims to examine neuroanatomical correlates of this semantic feature. This thesis reports three experiments investigating both the influence of animacy on the linearization of word order and its relational effect in sentence processing. Thereby, functional magnetic resonance imaging was used as a research method. Regarding the influence of animacy on the linearization of arguments, a sensitivity of the pars opercularis of the left inferior frontal gyrus (IFG) to violations of the animacy principle was demonstrated. In contrast to former accounts on the functional role of the pars opercularis that interpreted its sensitivity to complex sentence structures in terms of syntactic transformations or syntactic working memory costs, the present thesis provides strong evidence for a language-specific function of this region in the linearization of arguments. Thus, an activation increase in the pars opercularis was not only found when the syntactic linearization principle was violated (subject-before-object principle) but also when a principle concerning syntactic and semantic information was violated (thematic hierarchy principle) and even in case of violations of a purely semantic linearization principle (animacy principle). Furthermore, the posterior superior temporal sulcus (pSTS) of the left hemisphere was shown to engage in the processing of unmarked transitivity, which can be attributed to the relational impact of animacy information. Independent of argument order, there was always an activation increase in this cortical region when the critical sentences contained two animate arguments, thereby yielding an interpretation in terms of the relational role of animacy. This second experimental result is consistent with previous neuroanatomical data indicating an engagement of this cortical region when a mapping between syntactic and semantic argument hierarchies was not straightforwardly possible. Obviously, the pSTS can be associated with the interaction between syntactic and semantic information, in which the animacy of the arguments is of crucial importance with respect to their relation. Altogether, the present neuroanatomical data provide clear evidence for an influence of the semantic feature animacy on sentence processing. It is shown for the first time that a cortical region which has previously been exclusively associated with syntactic processing is also sensitive to this non-syntactic feature. In addition to the investigation of specific linguistic questions, an empirical approach like the present provides the opportunity for a more fine-grained development of sentence processing models on the basis of behavioral, neurophysiological and neuroanatomical data