This collaborative and interdisciplinary research project seeks to clarify the dynamic balance between lectal coherence, linguistic variability, and language change: while the former is essential for structural integrity and social orientation, the latter two enable adaptation and differentiation. To this end, a group of researchers from diverse disciplines and universities, specialising in various fields of linguistics, have collaborated to address this issue. The researchers involved in this project hail from a diverse range of academic backgrounds, including but not limited to the fields of computational linguistics, machine learning and artificial intelligence research, quantitative linguistics, phonetics and speech processing, psycholinguistics, contact linguistics, dialectology, and variationist sociolinguistics.

You can get an overview of the researchers involved here: People
You can find an overview of the individual projects here: Projects

DETAILED SUMMARY OF THE PROJECT

The objective of this Research Unit is to investigate the interplay between linguistic variability and stability through the lens of lectal coherence. Lectal coherence refers to the extent to which linguistic variants – across all levels of the linguistic architecture – systematically co-occur within and across individual speakers (Guy & Hinskens 2016:2). It serves crucial communicative and cognitive functions, facilitating language processing, ensuring mutual intelligibility, enabling language acquisition, and supporting the construction of individual social and regional identities. The notion of lectal coherence offers a critical framework for understanding the relationship between language variation, perception, cognition, and change while also explaining how shared patterns of language use within a social group or historical context distinguish one lect or variety from another. Despite its significance, this concept remains relatively underexplored.

Although coherence is an integral property of all linguistic systems, manifesting in both language use and perception (see e.g. the papers in Beaman & Guy 2022), it has received limited theoretical and empirical attention. This is also true for psycholinguistics and in variationist sociolinguistics where the concept was originally developed (Weinreich, Labov & Herzog 1968:108). Prior research has shown that linguistic systems can be “more” or “less” coherent (e.g., “dialect mixing,” “koinéization,” “focusing,” “relocation,” “synchronization”); however, it remains unclear how much coherence is required for a system to persist and remain intelligible and stable. Does coherence follow from usage or must it reach a critical mass to prevent systemic fragmentation? Another major research gap concerns the relationship between individual-level coherence and group-level norms, particularly whether coherence is the driver or the result of shared linguistic behaviour. Critically, the mechanisms, degrees, and implications of coherence within a theory of language change remain insufficiently understood. This project seeks to clarify the dynamic balance between lectal coherence, linguistic variability, and language change: while the former is essential for structural integrity and social orientation, the latter two enable adaptation and differentiation.
To tackle the challenge of lectal coherence, this Research Unit addresses five core questions:

• How is lectal coherence structured within and across linguistic levels in individual speakers?
  Hypothesis: Coherence is largely driven by a cognitive preference for structural consistency, mitigated by socioindexicalities.
• How does linguistic coherence emerge at the group level from individual language use?
  Hypothesis: Social alignment amplifies coherence through perceptual salience, group identity, and accommodation.
• What is the perceptual and social impact of lectal coherence?
  Hypothesis: Higher levels of  lectal coherence enhance dialect recognisability and sociolinguistic indexicality.
• How is lectal coherence established in real-time interaction?
  Hypothesis: In inter-dialectal encounters, speakers dynamically exploit intra-lectal variability to create situational coherence through reciprocal accommodation (in line with Giles et al. [1973] theory of accommodation).
• How can advances in machine learning, NLP, and AI enhance our understanding of lectal coherence?
  Hypothesis: Machine learning enables the processing and analysis of vast linguistic datasets while also providing indirect measures of coherence based on model performance.

To answer these questions, this Research Unit takes a multi-disciplinary approach, bringing together sociolinguists, dialectologists, psycholinguists, computational linguists and specialists in phonetics, phonology, morphology, syntax, multilingualism, and language contact. This project aims to develop an integrated account of lectal coherence as a core force in linguistic stability and change, offering a theoretical model of lectal coherence which enables predictive analyses of language change.