Frontiers in Psychology (Apr 2014)
On-line Processing of German Number-marked Relative Clauses in the Visual-world Paradigm
Abstract
Introduction Individuals with aphasia (IWAs) often show above chance performance in the comprehension of subject relative clauses (SRCs) and chance performance for object relative clauses (ORCs) in off-line sentence-picture verification tasks (e.g., Burchert, De Bleser, & Sonntag, 2003). A similar subject-object asymmetry was observed in on-line measures, as evidenced by longer self-paced listening times for ORCs compared to SRCs (Caplan, Waters, Dede, Michaud, & Reddy, 2007). Chance performance on number-marked SRCs and ORCs in behavioral tests suggests that German IWAs, unlike healthy controls, do not exploit number morphology in RC interpretation (Burchert et al., 2003). To our knowledge, an investigation of number marking processing in RCs in on-line tasks has not been published yet. The present ongoing study focuses on German, a language in which SRCs and ORCs are strict minimal pairs in terms of word order. We investigate the off-line and on-line processing of RCs in IWAs and healthy controls using the visual world paradigm (VWP). The VWP allows examining sentence processing in real time and testing whether IWAs show normal-like on-line processing, even if the overall performance is at chance level. Methods Test sentences are 16 SRC (1) and 16 ORC (2) questions. Due to case syncretism, disambiguation occurs only sentence finally through number marking at the finite verb. Moreover, 32 questions with a prepositional phrase are used as fillers (3). (1) SRC: Wo ist das Schwein, das die Wölfe kitzelt? (Where is the pig that is tickling the wolves?) (2) ORC: Wo ist das Schwein, das die Wölfe kitzeln? (Where is the pig that the wolves are tickling?) (3) Filler: Wo ist das Schwein mit dem Ballon? (Where is the pig with the balloon?) All sentences are randomized and presented auditorily. Simultaneously, colored illustrations of animals performing an action are shown on a computer screen (see Figure 1). Participants have to identify via button press (left/right) the target animal to which the question refers. During this task, eye movements are collected as an on-line measure of sentence processing. Off-line comprehension is measured in terms of accuracy of target identification. Ten IWAs with sentence comprehension deficits and 30 healthy controls are tested. Discussion Following Burchert et al. (2003), we expect the IWA’s off-line comprehension of SRCs and ORCs to be at chance level, while controls make hardly any errors. In the on-line data, the number of fixations to the target picture are supposed to increase only at the verb or shortly after the sentence offset, since disambiguation occurs sentence finally at the verb. Controls are expected to show faster or longer fixations to the target in SRCs compared to ORCs (Caplan et al., 2007). In line with Hanne, Sekerina, Vasishth, Burchert, and De Bleser (2011), IWA’s fixations to the target should not differ qualitatively from those of controls, at least for correct responses, but eye gaze patterns may be delayed. Data collection and analysis is still ongoing. Results will be ready by October and presented and discussed at the Academy of Aphasia conference.
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