Martin Corley and colleagues played recordings of English sentences, which either did, or did not, include a hesitation before the final word, to 12 participants. The listeners had electrodes placed on their heads, so that the researchers could look out for a negative change in voltage over the centro-parietal region of the scalp – the N400 – which is typically observed when people have to process a word they aren’t expecting.
For example, given a spoken sentence stem like “Everyone’s got bad habits and mine is biting my…”, the final unexpected word “tongue” would usually be associated with the N400.
Crucially, the researchers found that a spoken hesitation “er…” before a sentence’s final word had the effect of reducing the difference in N400 observed for an unexpected final word compared with an expected one. It seems that the hesitation had made the unexpected word easier to process, although an alternative, less likely explanation is that the hesitation made expected words harder to process.
Hesitation also had an effect on the listeners’ memories. About 55 minutes after the listening part of the study, the same participants were presented with all 160 of the words that had come at the end of the experiment’s sentences, intermingled with 160 new words, with their task to say which words were new and which were old. The listeners were slightly, but significantly, more likely to correctly recognise final words that had come after a hesitation, than final words that had come at the end of a fluently spoken sentence.
These findings suggest hesitations might serve some advantages to public speakers. Orators like President Bush are mocked for their disfluent style, but perhaps by hesitating at strategic moments in his speech, Bush is hammering home key points.
Co-author on the study Lucy MacGregor said there could be some truth in this, but she had a couple of warnings for budding speakers thinking of adopting a stop-start style. First of all, too much disfluency will likely swamp listeners’ attentional systems. Also, past research has shown that speakers who hesitate are generally perceived to be less knowledgeable. “This means,” MacGregor said, “that although (used carefully/sparingly), hesitations may help listeners remember what a speaker has said, listeners may be left with a less than favourable impression of a speaker’s knowledge.”
Corley, M. MacGregor, L.J. & Donaldson, D.I. (2007). It’s the way that you, er, say it: Hesitations in speech affect language comprehension. Cognition, 105, 658-668.