What models explain how and why language changes spread?
Theories of language change: the wave and S-curve models, functional and random-fluctuation theories, lexical gaps, the substratum theory and named models of how change spreads.
A focused answer to the AQA A-Level English Language theory topic, covering the wave and S-curve models, functional theory, random fluctuation, lexical gaps, substratum theory and named models of how language change spreads, with reference to Hockett, Halliday and Aitchison.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this topic is asking
AQA wants you to apply named theories and models that explain how and why language change happens and spreads, and to use them to interpret data showing variation and change over time. The examiner reward is for application: a model named but not used to explain the data earns little, while a model matched precisely to a feature of the data earns the higher bands.
Models of how change spreads
These two models answer different questions and should not be confused. The wave model is about space (where a change reaches), while the S-curve is about time (how fast a population adopts it). A new pronunciation might be modelled by the wave (radiating from a city) and by the S-curve (its uptake graph) at once. Both describe diffusion rather than cause, so a strong answer pairs a spread model with a cause model.
Why change happens
These three are the cause models, and each fits different data. Functional theory is strongest for need-driven coinage: "to google" or "selfie" fill genuine lexical gaps. Substratum theory is strongest where contact is the obvious driver: Norse and Norman French influence on English, or modern Multicultural London English emerging from contact between communities. Random fluctuation is the model of last resort, for changes with no obvious functional or contact cause, treating them as arbitrary drift. Note that "random" is itself a theoretical claim, not an admission of ignorance: Hockett's point is that not all change is purposeful. Jean Aitchison adds the social dimension: innovations are typically led by particular groups and diffuse once they gain prestige, which links this topic back to the social meaning of variation and to attitudes.
Try this
- For a new word you know, decide whether functional theory, substratum theory or random fluctuation best explains it.
- Sketch why the wave model and the S-curve answer different questions about the same change.
- Use Aitchison to explain why a change led by a prestigious group spreads faster.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 202020 marksEvaluate the usefulness of different models in explaining how language change spreads. Refer to relevant theories and examples in your answer.Show worked answer →
A Paper 2 essay rewarding AO1, AO2 and AO4. Treat the models as tools with different strengths rather than ranking one as correct.
Set out the spread models: the wave model (geographical diffusion, weakening with distance) and the S-curve (rate of adoption over time, slow then fast then levelling). Then the cause models: Halliday's functional theory (change meets users' needs, fills lexical gaps), Hockett's random fluctuation (chance errors and instability), and substratum theory (contact with other languages). Evaluate by showing what each explains and misses: the wave model handles regional spread but not why a change starts; the S-curve charts uptake but not cause; functional theory explains need-driven coinage but not arbitrary shifts.
Conclude that the models are complementary, each capturing a different dimension. Markers reward named models, applied examples, and an evaluative comparison rather than a list.
AQA 202220 marksAnalyse the data on a recent language change and explain it using relevant theories of how and why language changes. Refer to appropriate concepts in your answer.Show worked answer →
A Paper 2 data response rewarding AO1, AO2 and AO3. Apply the models to the specific change in the data.
Describe the change (a new word, a grammatical shift, a spelling form in digital text). Explain why it arose: functional theory if it fills a lexical gap (a word for new technology), substratum theory if it comes from language contact, random fluctuation if it looks like an arbitrary drift. Explain how it spreads: the S-curve for its rate of adoption and the wave model if the data shows geographical patterning. Add Aitchison on how innovations are adopted and diffuse once they gain prestige.
Conclude with a model-anchored account of both cause and spread. Markers reward the right model matched to the right feature of the data, applied not just named.
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Sources & how we know this
- AQA A-level English Language (7702) specification — AQA (2015)