Linguists have been interested in several aspects of language variation: how language varies regionally, and also how it is used by different social groups and in different contexts. Of these, the study of regional variation has the longest academic history and is therefore perhaps a good place to begin.
The study of regional variation in English is sometimes known as dialectology.
Dialectologists have been interested in different pronunciations, words and grammatical structures used in different parts of the country: how a small river, for instance, is known as a burn in Scotland and parts of Northumberland, a beck in other parts of northern England and a brook or stream further south.
The Survey of English Dialects, running through the 1950s, asked speakers in different localities about the words, structures and pronunciations they used (e.g. 'What do you call any running water smaller than a river?').
This enabled researchers to establish geographical boundaries between different dialects, or, more usually, a 'dialect continuum' in which changes occurred gradually across an area.
Researchers could also look at any patterns in the distribution of related dialect features. Beck is an example of a Scandinavian loan word (it comes originally from Old Norse bekkr).
Such words of Scandinavian origin are concentrated in areas of the north of England that were heavily settled by Scandinavians around 1000 years ago.
Dialectologists have been able to document examples of language change. The word flayed, for instance, is found in isolated pockets in the north of England – speakers in neighbouring areas use the term frightened, or sometimes both flayed and frightened.
The hypothesis here is that flayed – another Scandinavian loan word - was once much more widespread but its use was gradually eroded as frightened took over. Change over time can also be shown by carrying out successive dialect surveys of the same area, or by surveying both older and younger speakers.
Using these methods, researchers in the south-east of England have identified a process of 'dialect levelling', whereby dialects lose some of their distinctive features and become more similar.
While the focus here is on British English, linguists have documented variation and change in other areas such as North America.
They have also studied differences between national varieties – e.g. the standardized varieties spoken in Britain, North America, Australia and New Zealand. And there is considerable contemporary interest in the 'New Englishes' spoken as second language varieties in countries such as Singapore, India and Nigeria, often influenced by local languages in these countries.
The study of 'traditional' British dialects focussed on a particular set of speakers, sometimes ironically referred to as NORMs (non-mobile, older, rural males).
Such speakers were regarded as the best informants on local varieties that, even in the 1950s, were in danger of dying out. More recently, researchers have become interested in urban varieties, and in documenting the variable language use of different social groups.
The area of linguistics that takes account of social aspects of language is termed sociolinguistics. Sociolinguists have identified relationships between language use and social categories such as class and gender.
A US researcher, William Labov, pioneered research in this area in the 1960s. Labov identified certain pronunciation features that varied within a community (in a famous study carried out in New York, this included whether or not speakers pronounced the 'r' in words such as part – a high status pronunciation in New York).
He interviewed a sample of speakers from different social class groups, structuring the interview carefully to elicit more, and less formal speech. Labov found that speakers from higher social classes pronounced 'r' more often, but also that all speakers used this pronunciation more frequently in formal speech.
There was therefore a systematic relationship between language use, formality and social class. Researchers in the USA, Britain and elsewhere have adapted Labov's methods to study how language use varies according to speakers' gender, ethnic group, age, how closely integrated they are into a local community, and the particular context in which they are speaking.
Researchers have also extended the study of language change to take account of social factors – for instance, identifying aspects of people's lifestyles that lead them to be more innovative or conservative as speakers.
Variation in context
By virtue of their association with certain social groups, language varieties acquire social meanings which people tap into as they speak. In speaking in a certain way, then, speakers may sound more or less northern, or middle class, or feminine.
Social psychologists have found additional meanings associated with language varieties – for instance, listeners associate English accents with different degrees of competence or social attractiveness. In changing the way they speak in different contexts, speakers may foreground, or play down, such aspects of their identities.
Some contemporary studies have focussed on how individuals vary their speech in this way. Rather than looking at large scale patterns of variation (e.g. social and contextual patterns in the pronunciation of 'r' in words like part) such studies attempt to capture variation 'on the hoof' – to look closely at how speakers adopt, and switch between different pronunciations, grammatical structures etc as they interact with others.
A study of a Cardiff DJ, for instance, found that he drew on a shifting range of pronunciations, highlighting a more or less local identity, and sometimes an American influence, at different points in his show.
Studies of bilingual speakers have also looked at how they adopt different languages, or switch between languages in different contexts.
Speakers may switch between English and Welsh in Wales, English and French in Canada or English, Swahili and Kikuyu in Kenya, allowing them to carry out a range of 'identity work' (highlighting, satirizing, subverting an English-speaking identity, or balancing competing identities) in interaction with others.