Exemplar-Based Speech Representation
PI: Grzegorz Dogil (former PI's Bernd Möbius and Hinrich Schütze)
Researchers: Jagoda Bruni, Daniel Duran, Michael Walsh (former member: Travis Wade)
Within the overarching topic of the SFB, Incremental Specification in Context, Exemplar Theory is a formal model of contextual perception and production. Thus, we use Exemplar Theory as a model of context that explicates how linguistic units are incrementally specified in production and to what degree the fully specified speech signal undergoes incremental processes of underspecification in perception.
The first phase of this project yielded two computational models which have facilitated the pursuit of the research agenda set out in the original A2 proposal. The first model, known as the Context Sequence Model, models speech perception by representing memory as a single ordered collection of acoustic cues from previously heard speech and encoded to preserve temporal patterns. The categorization of newly encountered speech sounds involves comparing the sounds, and their neighbouring contexts, with similar sequences in memory. The second model is the Mulit Level-Exemplar Model, whose key innovation is the explicit formalisation of the relationship between exemplars on the constituent level and exemplars on what is referred to as the unit level. Constituents are segments, for example, consonants and vowels in phonetics, and words in syntax. Units are represented by syllables in phonetics, and phrases or sentences in syntax. Both models have been succesful in accounting for a number of phenomena in phonetics and syntax.
In the second phase we have investigated how exemplars dynamically emerge from the speech stream (particularly from the perspective of learning correspondence between acoustics and articulation). Moreover, we have examined how well our models, developed in the first phase, capture linguistic abstraction. Additionally, we have examined the nature of relationship between exemplar storage and prosody and we have established at fine levels of phonetic detail the impact fo acquired phonetics on second language learning (in particular with respect to measuring effects of phonetic transfer and interference). The outcomes of these investigations can be summarized under topics of research listed below:
- exemplar constitution and multi-modal representations in the Context Sequence Model
- Exemplar Theory in prosody: temporal and tonal
- Exemplar Theory in language learning
- exemplar-theoretic language modelling