Robert Daland

Explaining sonority projection effects

The term sonority projection refers to behavioural distinctions speakers make between unattested phonological sequences on the basis of sonority. For example, among onset clusters, the well-formedness relation [bn]>[lb] is observed in speech perception, speech production and non-word acceptability (Davidson 2006 , 2007 , Berent et al. 2007 , Albright, ms). We begin by replicating the sonority projection effects in a non-word acceptability study. Then we evaluate the extent to which sonority projection is predicted by existing computational models of phonotactics (Coleman & Pierrehumbert 1997 , Hayes & Wilson 2008 , inter alia ). We show that a model based only on lexical statistics can explain sonority projection in English without a pre-existing sonority sequencing principle. To do this, a model must possess (i) a featural system supporting sonority-based generalisations, and (ii) a context representation including syllabification or equivalent information.

Linking speech errors and phonological grammars: Insights from Harmonic Grammar networks

Phonological grammars characterize distinctions between relatively well-formed (unmarked) and relatively ill-formed (marked) phonological structures. We review evidence that markedness influences speech error probabilities. Specifically, although errors result in both unmarked as well as marked structures, there is a markedness asymmetry: errors are more likely to produce unmarked outcomes. We show that stochastic disruption to the computational mechanisms realizing a Harmonic Grammar (HG) can account for the broad empirical patterns of speech errors. We demonstrate that our proposal can account for the general markedness asymmetry. We also develop methods for linking particular HG proposals to speech error distributions, and illustrate these methods using a simple HG and a set of initial consonant errors in English.

Variation in the input: a case study of manner class frequencies*

What are the sources of variation in the input, and how much do they matter for language acquisition? This study examines frequency variation in manner-of-articulation classes in child and adult input. The null hypothesis is that segmental frequency distributions of language varieties are unigram (modelable by stationary, ergodic processes), and that languages are unitary (modelable as a single language variety). Experiment I showed that English segments are not unigram; they exhibit a ‘bursty’ distribution in which the local frequency varies more than expected by chance alone. Experiment II showed the English segments are approximately unitary: the natural background variation in segmental frequencies that arises within a single language variety is much larger than numerical differences across varieties. Variation in segmental frequencies seems to be driven by variation in discourse topic; topic-associated words cause bursts/lulls in local segmental frequencies. The article concludes with some methodological recommendations for comparing language samples.

Loci and locality of informational effects on phonetic implementation

Abstract Recent evidence suggests that the phonetic realization of linguistic units is sensitive to informational context. For example, the duration of a word is shorter when it is probable given the following word. Word-specific phonetic variation is unexpected according to modular/feedforward models. We consider various challenges to identifying the loci of informational effects on phonetic implementation – do they arise in production, perception, memory, or some combination? Section 2 addresses a theoretical issue: what are the right measure(s) of predictability/informativity? An urgent direction for future work is to understand what kinds of context matter and why. Section 3 reviews second-mention reduction and other non-local discourse effects, which strongly suggest a production locus (rather than arising in speech perception or memory). Important future directions include modeling discourse/topic in corpus studies, and experimentally assessing the role of nonlocal context in perception and memory. Section 4 addresses the role of computational modeling. We call for integrated, implemented end-to-end models which include speech perception, lexical representation, and speech production components.

The role of the striatum in linguistic selection: Evidence from Huntington’s disease and computational modeling

Though accumulating evidence indicates that the striatum is recruited during language processing, the specific function of this subcortical structure in language remains to be elucidated. To answer this question, we used Huntingtons disease as a model of striatal lesion. We investigated the morphological deficit of 30 early Huntingtons disease patients with a novel linguistic task that can be modeled within an explicit theory of linguistic computation. Behavioral results reflected an impairment in HD patients on the linguistic task. Computational model-based analysis compared the behavioral data to simulated data from two distinct lesion models, a selection deficit model and a grammatical deficit model. This analysis revealed that the impairment derives from an increased randomness in the process of selecting between grammatical alternatives, rather than from a disruption of grammatical knowledge per se. Voxel-based morphometry permitted to correlate this impairment to dorsal striatal degeneration. We thus show that the striatum holds a role in the selection of linguistic alternatives, just as in the selection of motor and cognitive programs.

Toward a generative theory of language transfer: Experiment and modeling of sC prothesis in L2 Spanish

Abstract When native Spanish speakers produce English words with initial [s]-consonant clusters (sC), they sometimes produce a prothetic vowel, e.g. stigma > estigma. This paper reports a production experiment on this phenomena, as well as computational modelling of the experimental results. Carlisle (1991a) proposed the ‘resyllabification account’ in which prothesis is a language transfer effect, whose essential motivation is to satisfy L1/Spanish syllable phonotactics. Replicating all previous work, a greater rate of prothesis was found in postconsonantal contexts than in postvocalic contexts (Rick (e)stinks > Ricky (e)stinks). A novel prediction is that when prothesis occurs, the [s] should have durational characteristics associated with the coda position, whereas it should have onset characteristics when prothesis does not occur; this was found. Another prediction is that a grammar which captures the variability in prothesis should in some sense be “between” the L1/Spanish and L2/English grammars. This latter prediction was tested by developing a constraint-based analysis of sC prothesis in Maximum Entropy Harmonic Grammar (Goldwater & Johnson, 2003). The results were consistent with a view of language transfer as ‘linear interpolation’ of constraint weights, conditioned on an ‘effort’ constraint reflecting how phonological planning varies with task/ modality demands.