How does stress affect your public speaking skills?

Post written by guest host Dr Pete Etchells, Lecturer in Psychology at Bath Spa University and Science Blog Co-ordinator for The Guardian.

Having to give a talk or a speech in front of a large group of people is one of the scarier things we might find ourselves having to do at some point in our lives. In those situations, ideally we want to give a flawless, well-rehearsed delivery, and getting too stressed is often linked to becoming – literally – lost for words. But is there any actual evidence for this link?

Tony Buchanan and colleagues have recently investigated what sort of aspects of speech and language are affected in stressful versus non-stressful situations. They asked 91 people to participate in a social stress test, in which they had five minutes to prepare a speech, and then immediately deliver it. In the stressful condition, they had to imagine that they had been accused of shoplifting, and had to prepare a defence that they would deliver to the 'store manager' (an experimenter). Immediately after the speech, they were given a difficult mental arithmetic task. In the non-stressful condition, people spent five minutes preparing a summary of a travel article, which they then had to read aloud to a video camera. Immediately after, they completed a much simpler arithmetic task.

Buchanan's team measured levels of the stress hormone cortisol in samples of saliva taken before the test, plus 10 and 30 minutes afterwards. They also measured heart rate, the speed at which people spoke during their speech, as well as the number of pauses and the number of 'nonfluencies' – words like um, er, and hmm.

The stressful speech condition seemed to increase stress levels – the measures of heart rate and cortisol levels showed an increase in this condition compared to the non-stressful situation. However, some of the speech variables that the researchers looked at didn't seem to be affected in the way that you might expect. Regardless of the stress condition, the speed at which people talked during their speech didn't differ. Strangely, the number of nonfluencies was higher for the non-stressful speech than in the stressful one. The only detrimental thing that stress seemed to have an effect on was pause time – as they progressed through their speech, people tended to stop increasingly more often in the stressful condition as opposed to the non-stressful condition.

Buchanan and his colleagues acknowledge the limitations of their study – as it's correlational in nature, we can't say for sure whether increases in cortisol levels cause a greater number of pauses in speech production, or whether noticing that you're pausing more often in the task causes your cortisol levels to increase.

That being said, it seems like pause time is important, because it is thought to be an indication of lexical retrieval processes – if more thought is required for a certain part of a speech, or harder words need to be used, you're more likely to stop for a moment before saying them. In stressful situations, these retrieval processes take a longer time, and so you're more prone to pausing. So this study seems like an interesting step forward in understanding specifically how stress affects different aspects of speech production – you might even say it gives us pause for thought.

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Buchanan, T., Laures-Gore, J., & Duff, M. (2014). Acute stress reduces speech fluency Biological Psychology, 97, 60-66 DOI: 10.1016/j.biopsycho.2014.02.005