Evidence for the role of German final devoicing in pre-attentive speech processing: a mismatch negativity study.

Results of a mismatch negativity experiment are reported in which the pre-attentive relevance of the German phonological alternation of final devoicing (FD) is shown in two ways. The experiment employs pseudowords. (1) A deviant [vus] paired with standard /vuzə/ did not show a mismatch effect for the voicing change in /z/ versus [s] because the two can be related by FD. When standard and deviant were reversed, the two could not be related by FD and a mismatch effect for the voicing difference occurred. (2) An ill-formed deviant that violates FD, *[vuz], triggered mismatch effects that were plausibly attributed to its ill-formedness. The results show that a syllable-related process like FD is already taken into account by the processing system in early pre-attentive processing.

Brain response to prosodic boundary cues depends on boundary position.

Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer's syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well-understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP) study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name) as compared to later in the utterance (i.e., after the second name). A closure positive shift (CPS)-marking the processing of a prosodic phrase boundary-was elicited for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context.

Neural processing of acoustic duration and phonological German vowel length: time courses of evoked fields in response to speech and nonspeech signals.

Recent experiments showed that the perception of vowel length by German listeners exhibits the characteristics of categorical perception. The present study sought to find the neural activity reflecting categorical vowel length and the short-long boundary by examining the processing of non-contrastive durations and categorical length using MEG. Using disyllabic words with varying /a/-durations and temporally-matched nonspeech stimuli, we found that each syllable elicited an M50/M100-complex. The M50-amplitude to the second syllable varied along the durational continuum, possibly reflecting the mapping of duration onto a rhythm representation. Categorical length was reflected by an additional response elicited when vowel duration exceeded the short-long boundary. This was interpreted to reflect the integration of an additional timing unit for long in contrast to short vowels. Unlike to speech, responses to short nonspeech durations lacked a M100 to the first and M50 to the second syllable, indicating different integration windows for speech and nonspeech signals.

Mismatch negativity (MMN) to successive deviants within one hierarchically structured auditory object.

The Mismatch Negativity (MMN), a component of the event-related potential (ERP), is elicited by a deviant following a series of standard stimuli. The present study addressed the question whether two deviants occurring successively in one hierarchically organized auditory object would elicit separate MMN responses. An example of such an object is a VC syllable (vowel+consonant). In a passive oddball protocol, the syllables [ɔx] and [ɛʃ] were presented both as standards and deviants so that both phonemes, the vowel and the consonant, changed in the respective deviant. Two negative responses were found in the deviant-minus-standard difference waves. Due to the latencies these effects could not be interpreted as separate MMN responses to the phonemic changes. Instead, the first effect (108ms) was taken as an N1 modulation whereas the second negativity (168ms) was interpreted as an MMN mainly reflecting the change of the initial vowel. Furthermore, the present data were statistically compared with related results from Steinberg et al. (2010a, b) obtained partly from the same stimuli presented in oddball blocks with simple mono-phonemic deviances due to changing vowels. Higher MMN amplitudes were found for the syllable [ɛʃ] in the present data compared to those previous findings. Although this difference was only present for one of the stimulus syllables, it is discussed as a possible indicator of an anticipatory MMN enhancement due to the predictability of the second change in the deviant of the present experiment.

The role of stimulus cross-splicing in an event-related potentials study. Misleading formant transitions hinder automatic phonological processing.

The mental organization of linguistic knowledge and its involvement in speech processing can be investigated using the mismatch negativity (MMN) component of the auditory event-related potential. A contradiction arises, however, between the technical need for strict control of acoustic stimulus properties and the quest for naturalness and acoustic variability of the stimuli. Here, two methods of preparing speech stimulus material were compared. Focussing on the automatic processing of a phonotactic restriction in German, two corresponding sets of various vowel-fricative syllables were used as stimuli. The former syllables were naturally spoken while the latter ones were created by means of cross-splicing. Phonetically, natural and spliced syllables differed with respect to the appropriateness of coarticulatory information about the forthcoming fricative within the vowels. Spliced syllables containing clearly misleading phonetic information were found to elicit larger N2 responses compared to their natural counterparts. Furthermore, MMN results found for the natural syllables could not be replicated with these spliced stimuli. These findings indicate that the automatic processing of the stimuli was considerably affected by the stimulus preparation method. Thus, in spite of its unquestioned benefits for MMN experiments, the splicing technique may lead to interference effects on the linguistic factors under investigation.

How each prosodic boundary cue matters: evidence from german infants.

Previous studies have revealed that infants aged 6-10 months are able to use the acoustic correlates of major prosodic boundaries, that is, pitch change, preboundary lengthening, and pause, for the segmentation of the continuous speech signal. Moreover, investigations with American-English- and Dutch-learning infants suggest that processing prosodic boundary markings involves a weighting of these cues. This weighting seems to develop with increasing exposure to the native language and to underlie crosslinguistic variation. In the following, we report the results of four experiments using the headturn preference procedure to explore the perception of prosodic boundary cues in German infants. We presented 8-month-old infants with a sequence of names in two different prosodic groupings, with or without boundary markers. Infants discriminated both sequences when the boundary was marked by all three cues (Experiment 1) and when it was marked by a pitch change and preboundary lengthening in combination (Experiment 2). The presence of a pitch change (Experiment 3) or preboundary lengthening (Experiment 4) as single cues did not lead to a successful discrimination. Our results indicate that pause is not a necessary cue for German infants. Pitch change and preboundary lengthening in combination, but not as single cues, are sufficient. Hence, by 8 months infants only rely on a convergence of boundary markers. Comparisons with adults' performance on the same stimulus materials suggest that the pattern observed with the 8-month-olds is already consistent with that of adults. We discuss our findings with respect to crosslinguistic variation and the development of a language-specific prosodic cue weighting.

Phonotactic constraint violations in German grammar are detected automatically in auditory speech processing: a human event-related potentials study.

In this human ERP study, effects of language-specific phonotactic restrictions on automatic auditory speech processing were investigated by means of the dorsal fricative assimilation (DFA) that is obligatory in German grammar. Using a multiple passive oddball paradigm, we studied the deviance-related processing of phonotactically ill-formed strings violating DFA. Eight VC-syllables were created by exhaustively combining the vowels [Y,..,...,...] and the dorsal fricatives [Ç X], resulting in four well-formed and four ill-formed stimuli that were contrasted in oddball blocks with changing probabilities of occurrence. Only the ill-formed deviants elicited a negative ERP deflection maximal at about 100 msec after the onset of the fricative. This negativity is considered to reflect a phonotactic evaluation process requiring the activation of implicit phonotactic knowledge from long-term memory and resulting in the automatic detection of a DFA violation.

Activation and application of an obligatory phonotactic constraint in German during automatic speech processing is revealed by human event-related potentials.

In auditory speech processing, implicit linguistic knowledge is activated and applied on phonetic and segment-related phonological processing level even if the perceived sound sequence is outside the focus of attention. In this study, the effects of language-specific phonotactic restrictions on pre-attentive auditory speech processing were investigated, using the Mismatch Negativity component of the human event-related brain potential. In German grammar, the distribution of the velar and the palatal dorsal fricative is limited by an obligatory phonotactic constraint, Dorsal Fricative Assimilation, which demands that a vowel and a following dorsal fricative must have the same specifications for articulatory backness. For passive oddball stimulation, we used three phonotactically correct VC syllables and one incorrect VC syllable, composed of the vowels [epsilon] and [open o] and the fricatives [ç] and []. Stimuli were contrasted pairwise in experimental oddball blocks in a way that they differed in regard to their respective vowel but shared the fricative. Additionally to the usual Mismatch Negativity which is attributable to the change of the initial vowel and which was elicited by all deviants, we observed a second negative deflection in the deviant ERP elicited by the phonotactically ill-formed syllable only. This negativity cannot be attributed to any acoustical or phonemic difference between standard and deviant, it rather reflects the effect of a phonotactic evaluation process after both sounds of the syllable were identified. Our finding suggests that implicit phonotactic knowledge is activated and applied even outside the focus of the participants' attention.

Preattentive phonotactic processing as indexed by the mismatch negativity.

Processing of an obligatory phonotactic restriction outside the focus of the participants' attention was investigated by means of ERPs using (reversed) experimental oddball blocks. Dorsal fricative assimilation (DFA) is a phonotactic constraint in German grammar that is violated in *[epsilonx] but not in [open ox], [epsilonintegral], and [open ointegral]. These stimulus sequences engage the auditory deviance detection mechanism as reflected by the MMN component of the ERP. In Experiment 1 (n = 16), stimuli were contrasted pairwise such that they shared the initial vowel but differed with regard to the fricative. Phonotactically ill-formed deviants elicited stronger MMN responses than well-formed deviants that differed acoustically in the same way from the standard stimulation but did not contain a phonotactic violation. In Experiment 2 (n = 16), stimuli were contrasted such that they differed with regard to the vowel but shared the fricative. MMN was elicited by the vowel change. An additional, later MMN response was observed for the phonotactically ill-formed syllable only. This MMN cannot be attributed to any phonetic or segmental difference between standard and deviant. These findings suggest that implicit phonotactic knowledge is activated and applied in preattentive speech processing.