Robust Processing of Natural Language

Previous approaches to robustness in natural language processing usually treat deviant input by relaxing grammatical constraints whenever a successful analysis cannot be provided by ``normal'' means. This schema implies, that error detection always comes prior to error handling, a behaviour which hardly can compete with its human model, where many erroneous situations are treated without even noticing them. The paper analyses the necessary preconditions for achieving a higher degree of robustness in natural language processing and suggests a quite different approach based on a procedure for structural disambiguation. It not only offers the possibility to cope with robustness issues in a more natural way but eventually might be suited to accommodate quite different aspects of robust behaviour within a single framework.Comment: 16 pages, LaTeX, uses pstricks.sty, pstricks.tex, pstricks.pro, pst-node.sty, pst-node.tex, pst-node.pro. To appear in: Proc. KI-95, 19th German Conference on Artificial Intelligence, Bielefeld (Germany), Lecture Notes in Computer Science, Springer 199

Disentangling phonological well-formedness and attestedness

Disentangling the roles of phonological well-formedness and lexical attestedness in phonotactic processing has proven challenging. In this study, we present results from a passive listening ERP study showing that English speakers exhibit distinct neural responses to CCVC nonce words according to the phonological well-formedness and attestedness (in English) of the onset cluster. Clusters with poor sonority sequencing evoked an N400 effect compared to those without poor sonority sequencing, regardless of whether the well-formed clusters were attested in English. In contrast, unattested clusters, regardless of whether they were well-formed or ill-formed in terms of sonority sequencing, evoked a late positivity compared to attested clusters. The results suggest that listeners first perform a phonological analysis on potential words before submitting them to a lexical search

Stochastic phonological grammars and acceptability

In foundational works of generative phonology it is claimed that subjects can reliably discriminate between possible but non-occurring words and words that could not be English. In this paper we examine the use of a probabilistic phonological parser for words to model experimentally-obtained judgements of the acceptability of a set of nonsense words. We compared various methods of scoring the goodness of the parse as a predictor of acceptability. We found that the probability of the worst part is not the best score of acceptability, indicating that classical generative phonology and Optimality Theory miss an important fact, as these approaches do not recognise a mechanism by which the frequency of well-formed parts may ameliorate the unacceptability of low-frequency parts. We argue that probabilistic generative grammars are demonstrably a more psychologically realistic model of phonological competence than standard generative phonology or Optimality Theory.Comment: compressed postscript, 8 pages, 1 figur

Language Universals Engage Broca's Area

It is well known that natural languages share certain aspects of their design. For example, across languages, syllables like blif are preferred to lbif. But whether language universals are myths or mentally active constraints—linguistic or otherwise—remains controversial. To address this question, we used fMRI to investigate brain response to four syllable types, arrayed on their linguistic well-formedness (e.g., blif≻bnif≻bdif≻lbif, where ≻ indicates preference). Results showed that syllable structure monotonically modulated hemodynamic response in Broca's area, and its pattern mirrored participants' behavioral preferences. In contrast, ill-formed syllables did not systematically tax sensorimotor regions—while such syllables engaged primary auditory cortex, they tended to deactivate (rather than engage) articulatory motor regions. The convergence between the cross-linguistic preferences and English participants' hemodynamic and behavioral responses is remarkable given that most of these syllables are unattested in their language. We conclude that human brains encode broad restrictions on syllable structure

A model of sonority based on pitch intelligibility

Synopsis: Sonority is a central notion in phonetics and phonology and it is essential for generalizations related to syllabic organization. However, to date there is no clear consensus on the phonetic basis of sonority, neither in perception nor in production. The widely used Sonority Sequencing Principle (SSP) represents the speech signal as a sequence of discrete units, where phonological processes are modeled as symbol manipulating rules that lack a temporal dimension and are devoid of inherent links to perceptual, motoric or cognitive processes. The current work aims to change this by outlining a novel approach for the extraction of continuous entities from acoustic space in order to model dynamic aspects of phonological perception. It is used here to advance a functional understanding of sonority as a universal aspect of prosody that requires pitch-bearing syllables as the building blocks of speech. This book argues that sonority is best understood as a measurement of pitch intelligibility in perception, which is closely linked to periodic energy in acoustics. It presents a novel principle for sonority-based determinations of well-formedness – the Nucleus Attraction Principle (NAP). Two complementary NAP models independently account for symbolic and continuous representations and they mostly outperform SSP-based models, demonstrated here with experimental perception studies and with a corpus study of Modern Hebrew nouns. This work also includes a description of ProPer (Prosodic Analysis with Periodic Energy). The ProPer toolbox further exploits the proposal that periodic energy reflects sonority in order to cover major topics in prosodic research, such as prominence, intonation and speech rate. The book is finally concluded with brief discussions on selected topics: (i) the phonotactic division of labor with respect to /s/-stop clusters; (ii) the debate about the universality of sonority; and (iii) the fate of the classic phonetics–phonology dichotomy as it relates to continuity and dynamics in phonology

The structure of self-repairs in the speech of Hungarian learners of English

The study reported in the paper investigates the structure of L2 self-corrections in the speech of 30 Hungarian learners of English and 10 Hungarian native speakers. The aim of the research is to examine what the well-formedness of the corrections, the use of editing terms, the placement of cut-off points and the effect of the participants' level of proficiency on the structure of self-repairs reveal about the psycholinguistic processes of speech production. The results of the study lend additional support for modular models of speech production (e.g., Levelt 1983, 1989; Levelt et al. 1999) and reveal an important role of pragmatic constraints in psycholinguistic processing

Disentangling phonological well-formedness and attestedness: An ERP study of onset clusters in English

Disentangling the roles of phonological well-formedness and lexical attestedness in phonotactic processing has proven challenging. In this study, we present results from a passive listening ERP study showing that English speakers exhibit distinct neural responses to CCVC nonce words according to the phonological well-formedness and attestedness (in English) of the onset cluster. Clusters with poor sonority sequencing evoked an N400 effect compared to those without poor sonority sequencing, regardless of whether the well-formed clusters were attested in English. In contrast, unattested clusters, regardless of whether they were well-formed or ill-formed in terms of sonority sequencing, evoked a late positivity compared to attested clusters. The results suggest that listeners first perform a phonological analysis on potential words before submitting them to a lexical search