Johannes Knaus

The influence of rhythmic (ir)regularities on speech processing: Evidence from an ERP study on German phrases

The present study investigates the status of rhythmic irregularities occurring in natural speech and the importance of rhythmic alternations in cognitive processing. Previous studies showed the relevance of rhythm for language processing, but there has been only little research using the method of event-related potentials to investigate this phenomenon in a natural metrical context. To this end, an experiment was conducted in which the so-called Rhythm Rule (alternation of stressed and unstressed syllables) was either met or violated by stress clashes or stress lapses which are known to occur in German. The comparison of rhythmic well-formed conditions with the conditions including rhythmic irregularities revealed biphasic EEG-patterns for rhythmically marked structures, i.e., stress clashes and lapses. The present results show that irregular but possible rhythmic variants are costly in language processing, reflected by an early negativity and an N400 in contrast to the well-formed control conditions. Supposedly, the early negativity reflects error detection in rhythmical structure and supports the view that the brain is sensitive to subtle violations of rhythmical structure. A late positive component reflects the evaluation process related to the task requirements. The study shows that subtle rhythmical deviations from the Rhythm Rule are perceived and treated differently from well-formed structures during processing, even if the deviation in question is permitted and can therefore occur in language production.

Event-related Potentials Reflecting the Processing of Phonological Constraint Violations

How are violations of phonological constraints processed in word comprehension? The present article reports the results of an event-related potentials (ERP) study on a phonological constraint of German that disallows identical segments within a syllable or word (CC iVCi). We examined three types of monosyllabic CCVC words: (a) existing words ( p k), (b) wellformed novel words ( p f), and (c) illformed novel words ( p p) as instances of Obligatory Contour Principle (OCP) violations. Wellformed and illformed novel words evoked an N400 effect in comparison to existing words. In addition, illformed words produced an enhanced late posterior positivity effect compared to wellformed novel words. Our findings support the well-known observation that novel words evoke higher costs in lexical integration (reflected by N400 effects). Crucially, modulations of a late positive component (LPC) show that violations of phonotactic constraints influence later stages of cognitive processing even when stimuli have already been detected as non-existing. Thus, the comparison of electrophysiological effects evoked by the two types of non-existing words reveals the stages at which phonologically based structural wellformedness comes into play during word processing.

Processing (un-)predictable word stress: ERP evidence from Turkish

This paper investigates the way the predictability of prosodic patterns in a particular language influences the processing of stress information by native speakers of that language. We extend previous findings where speakers of languages with predictable stress had difficulties to process and represent stress information when confronted with a language with distinctive stress and investigate how the co-existence of a predictable stress pattern and exceptions to that regularity within a single language influences prosodic processing. The stress system of Turkish constitutes an instructive test case since it employs predictable stress on the final syllable of a prosodic word (e.g., mısır “corn”) and some exceptional nonfinal stress (e.g., mısır “Egypt”). Results from an event-related potential (ERP) study on stress violations in Turkish trisyllabic words showed asymmetrical ERP responses for different stress violations: Stress violations with final stress produced an N400 effect whereas violations with nonfinal stress produced a P300 effect. The application of the predictable pattern to words with lexical stress led to lexical costs and the application of exceptional stress to words with default stress to effects reflecting the evaluation of this pattern. Although final stress constitutes no alternative pattern for words with exceptional stress, participants have difficulties to judge this pattern as incorrect. In contrast, exceptional stress patterns are detected easily when applied incorrectly to words that normally receive final stress. These findings demonstrate nicely the co-existence of two phonological processing routines in Turkish speakers. Furthermore, the variability of stress patterns does not affect prosodic processing in general but instead leads to differential effects in stress perception. We conclude that stress predictability does not homogenously result in the so-called “stress deafness” effects in stress processing, but that it rather emerges only for the default stress pattern.

Stress “deafness” in a Language with Fixed Word Stress: An ERP Study on Polish

The aim of the present contribution was to examine the factors influencing the prosodic processing in a language with predictable word stress. For Polish, a language with fixed penultimate stress but several well-defined exceptions, difficulties in the processing and representation of prosodic information have been reported (e.g., Peperkamp and Dupoux, 2002). The present study utilized event-related potentials (ERPs) to investigate the factors influencing prosodic processing in Polish. These factors are (i) the predictability of stress and (ii) the prosodic structure in terms of metrical feet. Polish native speakers were presented with correctly and incorrectly stressed Polish words and instructed to judge the correctness of the perceived stress patterns. For some stress violations, an early negativity was found which was interpreted as a reflection of an error-detection mechanism. In addition, exceptional stress patterns (=antepenultimate stress) and post-lexical (=initial) stress evoked a task-related positivity effect (P300) whose amplitude and latency is correlated with the degree of anomaly and deviation from an expectation. In contrast, violations involving the default (=penultimate stress) did not produce such an effect. This asymmetrical result is interpreted to reflect that Polish native speakers are less sensitive to the default pattern than to the exceptional or post-lexical patterns. Behavioral results are orthogonal to the electrophysiological results showing that Polish speakers had difficulties to reject any kind of stress violation. Thus, on a meta-linguistic level Polish speakers appeared to be stress-“deaf” for any kind of stress manipulation, whereas the neural reactions differentiate between the default and lexicalized patterns.

The role of phonotactic principles in language processing

ABSTRACT The paper reports the results of a learnability experiment with German speakers, investigating the role of universal phonotactic constraints and language use in language processing. Making use of an artificial language paradigm, participants learned nonce words with existent and non-existent German final consonant clusters adhering to or violating sonority sequencing principles postulated for consonant clusters. Behavioural data and event-related brain potentials in response to these cluster properties were obtained twice, before and after learning word-picture-pairs. The results show (1) that learning and processing of final consonant clusters is facilitated by adherence to the sonority hierarchy, and (2) that actual existence of well- and ill-formed consonant clusters aids processing mechanisms. Thus, both implicit knowledge of universal phonotactic principles and frequency-based factors are demonstrated to play a role in the online-processing of words.

The role of predictability and structure in word stress processing: an ERP study on Cairene Arabic and a cross-linguistic comparison

This article presents neurolinguistic data on word stress perception in Cairene Arabic, in comparison to previous results on German and Turkish. The main goal is to investigate how central properties of stress systems such as predictability of stress and metrical structure are reflected in the prosodic processing of words. Cairene Arabic is a language with a regular foot-based word stress system, leading to highly predictable placement of word stress. An ERP study on Cairene Arabic is reported, in which a stress violation paradigm is used to investigate the factors predictability of stress and foot structure. The results of the experiment show that for Cairene Arabic the internal structure of prosodic words in terms of feet determines prosodic processing. This structure effect is complemented by a frequency effect for stress patterns.