The most frequent three-word phrase in both British and American spoken English turns out to be I don’t know, according to corpus research.
Lynn E Grant’s work reveals why we use this little phrase so often. It would be reasonable to expect it to indicate that the speaker can’t give the information they’ve been asked for, as in example (1) in the box. In fact, though, Grant’s analyses of the spoken component of the British National Corpus (BNC) and the New Zealand Wellington Corpus (WSC) finds that we use I don’t know more often as an ‘affective device’ to convey our feelings or as an ‘epistemic’ device to show how confident we are about the truth of what we are saying.
Example (2) shows its use as an affective device. Here I don’t know softens disagreement. It can also soften an assessment, as in (3). Grant points out that in both cases the phrase is a politeness marker, toning down a remark that could be seen as face threatening.
In (4) I don’t know is an epistemic device, acting as a polite hedge to avoid commitment.
It can also downplay a compliment, as in (5). As Grant explains, English speakers can feel uncomfortable when they receive a compliment, and a common response is I don’t know.
The shortened form I dunno or simply dunno has the same pragmatic functions, though overall speakers mainly use it as a polite hedge, to show uncertainty.
Grant uncovers some interesting differences between speakers of New Zealand English and speakers of British English. New Zealanders use I don’t know more often to avoid disagreement and to avoid committing themselves to their answers. And although in both the British English corpus and the New Zealand corpus I don’t know often occurs with a discourse marker (especially oh, I mean, you know and well), for New Zealanders the discourse marker is more likely to be oh, whereas for British English speakers it is more likely to be well. The reasons remain a mystery.
Grant concludes that there are implications here for language learning and language teaching. Language learners use I don’t know less often than native speakers do, and when they do use the phrase, it is not for the same functions. Even advanced learners of English, she maintains, need to be specifically taught how we use chunks like I don’t know in spoken English, since the meanings they create in discourse are fundamental to successful human interaction.
Grant, Lynn E. (2010). A corpus comparison of the use of I don’t know by British and New Zealand speakers. Journal of Pragmatics 42: 2282-2296.
This summary was written by Jenny Cheshire