I is for Intelligibility

28 05 2017

man on phoneI phoned my Spanish internet provider the other day and tried to explain a problem I was experiencing. Clearly, I was unintelligible because the operator immediately switched me to an English-speaking operator. Even then, I had trouble getting my message across, because I didn’t know how to say ‘tráfico de datos’ in English. Was I again being unintelligible, or simply incomprehensible?

This reminded me that, in a session on my MA TESOL course last summer, during a discussion on the goals of pronunciation teaching, one student mentioned the fact that she’d heard that there was a distinction between intelligibility and comprehensibility, and she asked me to explain the difference.

I volunteered an off-the-cuff explanation (as one does!), suggesting that intelligibility is a function of speakers (and particularly of their pronunciation), while comprehensibility (invoking Krashen) is a function of texts. Or, put another way, output is (to a greater or lesser extent) intelligible, while input is (to a greater or lesser extent) comprehensible.

Even as I said this, I could see there were problems. Communication is by definition reciprocal, so is it possible to gauge either intelligibility or comprehensibility without reference to interlocutors – either listeners or readers? Moreover, whether listening to a speaker or reading a text, your degree of understanding is going to be experienced in a similar way: ‘I understand it a bit, a lot, or not at all.’

Since that awkward day (sorry, Autumn, my bad!), I’ve had a chance to research the difference.  For example, Munro, Derwing  and Morton (2006, p. 112), referencing earlier work by the first two authors, define intelligibility ‘as the extent to which a speaker’s utterance is actually understood’, whereas comprehensibility ‘refers to the listener’s estimation of difficulty in understanding an utterance’. (So I wasn’t entirely wrong, perhaps). They further distinguish both from accentedness, i.e. the degree to which the pronunciation of an utterance sounds different from an expected production pattern.’ And they add: ‘Although comprehensibility and accentedness are related to intelligibility, they are partially independent dimensions of L2 speech.  An utterance that is rated by a listener as “heavily accented,” for instance, might still be understood perfectly by the same listener.  Furthermore, two utterances that are fully intelligible might entail perceptibly distinct degrees of processing difficulty, such that they are rated differently for comprehensibility.’

On the other hand, and markedly differently, Nelson (2011), referencing papers by Smith (1992) and Smith and Nelson (1985), defines intelligibility as ‘word and/or utterance recognition, involving the sound system’, and comprehensibility as ‘word/utterance meaning, or locutionary force’. To further complicate matters, they introduce the term interpretability, i.e. ‘the meaning behind the word/utterance, or illocutionary force’.

MacKay (2002, p. 52) helpfully (?) unpacks these distinctions with an example:

If a listener recognises that the word salt is an English word rather than a Spanish word, English is then intelligible to him or her. If the listener in addition knows the meaning of the word, it is comprehensible, and if he or she understands that the phrase, ‘Do you have any salt?’, is intended to be a request for salt, then he or she is said to be able to interpret the language.

Put another way, if you’re having trouble understanding someone, it may be a case of not recognizing what they’re saying (likely their fault), or not knowing what they mean (probably your fault), or not knowing what their intention is (could be anyone’s fault). Going back to my exchange on the phone, I can sort of apply these distinctions, but I’m also wondering if accentedness was the reason why I was switched to the English-speaking operator, since the first operator made no attempt even to negotiate some sort of understanding. (Mercifully, in a subsequent conversation with yet another operator, I was actually congratulated on my Spanish – probably because, although heavily accented, I was intelligible. Or do I mean  comprehensible?)

cómo es carlosThis raises another issue related to intelligibility: that it is highly subjective. As Rajagopolan (2010, p. 467) argues, ‘No matter how one tries to define intelligibility from a neutral standpoint, the question that cries out for an answer is: “intelligible for who?”’ Why was I intelligible to one of my interlocutors but not to another? Was it, indeed, nothing to do with accent at all, but more to do with attitude? After all, it is not accents that are intelligible, it is people.  I never tire of quoting Bamgbose (1998) on the subject: ‘Preoccupation with intelligibility has often taken an abstract form characterized by decontextualised comparison of varieties. The point is often missed that it is people, not language codes, that understand one another” (quoted in Jenkins,  2007, p. 84). Thus, intelligibility may have as much to do with our overall impression of a speaker as it has to do with the intrusiveness of their accent (or lack thereof) – not dissimilar to the notion of ‘comfortable intelligibility’ (Kenworthy 1987) or ‘perceived fluency’ (Lennon 2000, cited in Götz 2013).

Either way, this doesn’t provide a lot of solace to those who have to assess a learner’s pronunciation, as in the kinds of oral tests favoured by many public exams nowadays, using descriptors such as these:

  • is easy to understand throughout; L1 accent has minimal effect on intelligibility
  • can generally be understood throughout, though mispronunciation of individual words or sounds reduces clarity at times

What are the chances that any two raters will agree?


Götz, S. (2013) Fluency in native and nonnative English speech. Amsterdam: John Benjamins.

Jenkins, J.  (2007) English as a Lingua Franca: Attitude and Identity. Oxford: Oxford University Press.

Kenworthy J (1987) Teaching English Pronunciation. Harlow:  Longman.

McKay, S. (2002) Teaching English as an International Language. Oxford: Oxford University Press.

Munro, M.J., Derwing, T.M., & Morton, S.L. (2006) ‘The mutual intelligibility of L2 speech.’ Studies in Second language Acquisition, 28.

Nelson, C. L. (2011). Intelligibility in World Englishes: Theory and Application. New York: Routledge.

Rajagopolan, K. (2010) ‘The soft ideological underbelly of the notion of intelligibility in discussions about “World Englishes”.’ Applied Linguistics, 31/3.

Smith, L. E. (1992). Spread of English and issues of intelligibility. In B. B. Kachru (ed.) The Other Tongue: English across Cultures (Second Edition). Urbana, IL: University of Illinois Press.

Smith, L. E. and Nelson, C. L. (1985). ‘International intelligibility of English: Directions and resources.’ World Englishes, 4(3).

Illustrations by Quentin Blake from Success with English, by Geoffrey Broughton, Penguin Education, 1968.