It is a universal truth—although not one universally acknowledged—that languages always change. Speech and writing are never entirely stable: new forms are always expanding in popularity and old ones dying out, the meanings of words and expressions are always shifting or being replaced by new ones, and particular pronunciations are always rising and falling in popularity. One area of research—indeed, the main area of research for many historical linguists—is the process by which these changes start.

In historical linguistics we use the term ‘innovation’ to describe the invention of a new form by a speaker. It’s obvious that every change that has even taken place (from the loss of the ‘wh’ sound /ʍ/ in English English to the replacement of the Middle English word bene by Middle French praere to mean ‘prayer’) as well as every change that is still ongoing (from ‘th-fronting’, the process by which the ‘th’ sound /θ/ is replaced by an ‘f’ sound /f/, to the use of ‘like’ to mark quoted speech) must once have been innovations. There must have been a first time and a first speaker for each of these changes: a first speaker to pronounce ‘wh’ /ʍ/ the same as ‘w’ /w/, a first speaker to use the then-French word praere instead of bene when speaking English, a first speaker to say ‘f’ /f/ for ‘th’ /θ/ and a first speaker to use ‘like’ to mark a quotation. We might ask—who were these speakers that have had such a great effect on the language? And why did they produce these innovations?

Innovation is actually happening all the time. All speakers use language creatively, frequently coining new words and using them just once in a particular context (‘nonce formations’), borrowing words from other languages to try to get across specific meanings (‘nonce borrowings’), producing slight differences in pronunciation or using words and phrases in subtly different ways than usual. This is both a blessing and a curse for the study of innovation. On the one hand, it means that it’s relatively easy to get data to study, either by trawling recordings of spoken language data or trying to prompt people to produce innovations in lab settings. However, the vast majority of these innovations never spread beyond the first speaker who uses them, and it’s vanishingly unlikely that the moment of innovation of any particular change which goes on to spread more widely will happen to be recorded. As a result, it’s practically impossible to study the process of innovation for successful changes.

Nevertheless, we can get some ideas about how innovations happen by studying unsuccessful innovations caught in corpora or in the lab, and by theorising about the changes which we observe spreading successfully.

Let’s start with the easiest of our examples. It’s pretty clear that borrowings (like the replacement of Middle English bene by praere) start life with bilingual speakers. In many communities of bilingual speakers, ‘code-switching’ (the use of multiple languages in the same utterance) is common. This gives one possible way in which a Middle French word could first have been used in an otherwise Middle English utterance. Alternatively, bilingual speakers could have chosen to start using the Middle French word rather than the Middle English one because it had subtly different connotations which they wanted to make use of. Or it might be that the word was particularly associated with a ‘domain’ (context) in which Middle French rather than Middle English was the normal language to use—this does appear to be true in this case, for the domain of religion. Once praere had starting turning up in the Middle English of bilingual speakers by one or any of these routes, monolingual Middle English speakers could simply hear it as a new word and start using it themselves. An interesting property of borrowing as a type of innovation is that clearly there’s no reason to assume that just one speaker did it first: as there were lots of bilingual speakers, many of them might have borrowed the form independently, making it all the more likely to spread to monolingual Middle English speakers.

A different possible source of innovations is speech errors. All speakers occasionally produce speech errors in all areas of language, and when a change looks like a form which could have been produced by a speech error, we must consider the possibility that that it started life as just such an error. In the case of the loss of the ‘wh’ sound, it was replaced by a sound which was very similar—the only difference between /ʍ/ and /w/ is that the former is voiceless and the latter voiced. This sound change might have started life by /ʍ/ being accidentally voiced, perhaps in a context when it was surrounded by other voiced sounds. Like the case of borrowing, there’s clearly no reason to assume that innovations of this type happened just once to one speaker. Instead, they might have started life in multiple places and times and with multiple speakers independently.

The above case was a ‘production error’—an error made by a speaker producing language. Other innovations might have started life as ‘perception errors’—errors made by listeners. The case of th-fronting might have started life as perception error. The ‘th’ /θ/ and ‘f’ /f/ sounds are not especially close in terms of how they are pronounced, and so it is relatively unlikely that one would be produced in error for the other. However, perceptually they are very close, so it is quite possible that a listener might have misheard a speaker and thought they were producing [f] for /θ/. Once this had happened, that listener might have gone on to actually produce [f]s for /θ/s, thinking that they were imitating the speaker they’d heard before.

Many researchers take a particular interest in innovations produced during the native acquisition of language by children. It’s clear that production and especially perception errors like those described above might be more likely to occur in child speech, and so many innovations of these types may have started during language acquisition. One special type of innovation can only happen during child language acquisition: ‘reanalysis’. Reanalysis takes place when the grammar of some piece of language is ambiguous and the learner comes to a different conclusion about what the grammar actually is than the speakers from whom they’re learning. Reanalysis has been subject to a huge amount of study in historical linguistics and is a tricky topic for which there isn’t really room here. If you’re interested, though, there’s lots of material online from which you can learn more.

All in all, we know of lots of different ways in which language changes can start. Nevertheless, determining conclusively what was the mechanism behind any specific innovation remains a difficult subject. The question of why certain innovations spread where the vast majority do not is an even thornier one, and perhaps a topic for a future blogpost…