Genre-specific parsing: Non-additive influences of metrical stress pattern on sentence processing
in collaboration with Ralf Rummer (Saarland University) In a self-paced reading experiment, we examined how metrical stress pattern affects the on-line processing and off-line comprehension of temporarily (subject/object) ambiguous sentences in German (see below). The sentences were disambiguated either towards a 'canonical' (subject-first, SO) or a 'non-canonical' (object-first, OS) sequence of grammatical functions. There were three groups of participants. The first two groups (A and B) were presented with sentences embedded in 'lyrical contexts'. In group A, all canonical (SO) structures implied a metrical irregularity at the disambiguating noun phrase and all non-canonical (OS) structures were metrically regular; in group B, it was the other way round (metrical irregularity in the OS condition; regular stress pattern in the SO condition). Participants in the third group (C) read the same sentences as in (A), but embedded in 'prosaic contexts' where no predictable metrical pattern is evoked. Fillers were also either lyrical (group A and B) or prosaic (group C), and they were always metrically regular. (See also http://www.coli.uni-sb.de/~chsc/Lyrics/Metric.pdf for further explication.) Context (A,B): Die Marktfrau hatte keine Zeit. Der Arzt lief zum Gericht. (A) SO: Dass Lisa [?] den Kommissar [acc] erkannte,... OS: Dass Lars [?] der Kommissar [nom] erkannte,... (B) SO: Dass Lars [?] den Kommissar [acc] erkannte,... OS: Dass Lisa [?] der Kommissar [nom] erkannte,... stand im Schlußbericht. Context (C): Die Marktfrau hatte kaum Zeit. Der Arzt ist vor Gericht gegangen. (C) SO: Dass Lisa [?] den Kommissar [acc] erkannte,... OS: Dass Lars [?] der Kommissar [nom] erkannte,... stand im Schlußbericht. We hypothesised that metrical irregularity would add some extra processing cost (as measurable in higher RTs) to the 'default' cost known from earlier work on subject-object asymmetries in German (e.g., Scheepers et al., 2000; Friederici et al., 2001). That is, we expected the garden path effect for non-canonical (OS) sequences to be weaker in group (A), but stronger in group (B) - relative to the prosaic control group (C). However, the results draw a strikingly different picture: the OS garden-path effect was significantly more severe in the prosaic condition (C) than in either of the two lyrical conditions (A or B), which, in turn, did not differ from one another in garden-path strength. What is more, participants in the lyrical conditions (A,B) performed reliably better on 'who-did-what-to-whom' comprehension questions after each trial than those in the prosaic condition (C), which strongly argues against a more 'shallow' understanding of target sentences in lyrical contexts. We conclude that reading is not substantially disrupted by metrical irregularity. Rather, a deviation from the canonical SO-sequence seems generally more tolerable in lyrical context than in prosaic context (without resulting in poorer understanding). This suggests that readers may employ genre-specific constraints: note that scrambled word orders are quite common in lyrical text (often driven by a desire to keep a well-formed metrical structure), but very rare in prosaic text. All in all, these results point to the importance of distinguishing between different text genres in order to describe the 'default' human sentence processing behaviour.