“This study outlines a corpus comparison of British and New Zealander speakers’ use of the phrases ‘I don’t know’ and ‘I dunno’. ”

Dr. Lynn Grant, who is a Senior Lecturer at the School of Languages and Social Sciences at the Auckland University of Technology, New Zealand ('The University for Changing the World') has recently completed a study which examined the linguistic properties of ‘I don’t know’ and ‘I dunno’. Finding that the phrases often find use as 'hedges', markers of uncertainty, and as politeness devices.

It was also determined that British speakers use the phrase with different frequency and sometimes for different reasons than New Zealand speakers do. Extensive though the project is, it is likely that the work on ‘Don’t know’ (and all its variants) is not yet fully completed.

“Further research could add to these findings by looking at all the meanings the phrases have in conversation, their use in academic discourse, as well as use of the single variant, ‘Dunno’. “

See: A corpus comparison of the use of I don’t know by British and New Zealand speakers in the Journal of Pragmatics ,Volume 42, Issue 8, August 2010, Pages 2282–2296

Also see:

Previous 'dunno' research  I dunno: A usage-based account of the phonological reduction of don’t in American English conversation Journal of Pragmatics, Volume 32, Issue 1, January 2000, Pages 105-124