Um, are you telling the truth?

Finding truth among  the lies?

You might suspect that someone is not telling the truth, but is there any way that you can be certain? Most people rely on intuition or they look for changes in body behaviour, such as fidgeting or breaking eye contact, but it seems that humans are not very efficient lie detectors and even those who have to make judgments about truth and deception as part of their professional role only perform at the level of chance. Some researchers have therefore turned their attention to more quantifiable cues that distinguish truth from deception and which do not rely on the human observer.

Researchers Gina Villar, Joanne Arciuli and David Mallard analysed the use of ‘um’ in the truthful and deceptive speech of a convicted murderer which he produced in two different contexts: when he was speaking in a formal media interview and when he was speaking in a (secretly taped) telephone conversation with his mistress. There are two hypotheses with regard to the use of ‘um’. One suggests that there would be an increased use of ‘um’ during deceptive speech because it reflects increased emotional and cognitive effort while telling a lie. The other hypothesis suggests that there would be a decreased use of ‘um’ during deceptive speech because deceivers might deliberately control their use of ‘um’ in order to appear more fluent and hence more credible. The researchers had found in a previous study that in laboratory elicited lies (where the lies were considered to be low-stake) participants had revealed a significantly decreased use of ‘um’ during deception and they wanted to see whether these results would be corroborated in real life data and where the lies were more high-stake.  

The researchers analysed the transcripts of four televised media interviews (each 20-30 mins long) and around 11 hours of secretly taped telephone conversations between the convicted murderer and his mistress (who had agreed to the conversations being taped). The transcripts were then carefully read in order to isolate all the utterances that could be verified as being either truthful or deceptive. Each sample was then coded for the presence of ‘um’ which was calculated as a percentage of the total number of words per sample.

The results clearly showed that ‘um’ was used less frequently in the deceptive speech compared to the truthful speech. The result held in both production contexts of the formal media interviews and the informal telephone conversations. The results, then, were in line with the researchers’ earlier findings with regard to low-stake laboratory elicited lies. While a single case study may not be generalizable to other persons, there is nevertheless some evidence from these results to suggest that a word such as ‘um’, which is often considered to be a ‘filler’ or unplanned error in speech, may be under the strategic control of the speaker.  The findings suggest that, in an attempt to successfully deceive, people can manipulate their linguistic behaviour and that ‘um’ may have a more important role in speech than many people realise.

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Villar, G., Arciuli, J. and Mallard, D. (2011). Use of “um” in the deceptive speech of a convicted murderer. Applied Psycholinguistics. 1-13.

doi:10.1017/S0142716411000117

This summary was written by Sue Fox