Lies and Cognition: How do we tell lies and can we detect them?

The aims of the present thesis are twofold. Firstly, to examine the particular cognitive processes that are involved in telling lies, and how they differ from those involved in telling the truth, in a variety of different circumstances. Secondly, to examine the
different factors that affect human ability to detect deception, with a particular focus on individual and cultural differences in both detection accuracy and response bias.

In relation to the first aim, a minimalist approach was taken, which allowed us to examine the contribution of individual cognitive processes to telling a lie. A simple computer task was developed, whereby participants lied and told the truth regarding the colour of a square and their vocal response times recorded. Response times have been shown to be greater when individuals lie compared to when they tell the truth, which supports the idea that additional processes are required in order to tell a lie. The relative contribution of these processes, and the factors that may affect this, remain unknown. Our experiments allow for an extension of previous work regarding the theoretical understanding of why telling a lie is more difficult than telling the truth, as well as the factors that may decrease or increase this difference. Since our experiments demonstrated that telling a lie does involve additional processes compared to telling the truth, and that this is reflected in measurable behavioural differences, our second aim was to examine the judgement factors that may affect the ability to identify this enhanced difficulty and accurately detect deception.

In relation to the second aim, human ability to detect deception was examined through the creation of video statements of individuals both truthfully and falsely describing an image they had previously viewed on a computer screen. Some of these statements were provided by individuals of the same cultural background as the judge, whilst others were provided by individuals of a different cultural background to the judge. Judges viewed these statements and evaluated whether they thought each one was truthful or a lie, as well as completing a variety of individual difference measures related to the ability to correctly interpret the behaviour and mental states of others. These experiments allowed us to examine possible relationships between both individual difference measuresand cultural background, on response bias and judgement accuracy, thus extending previous judgement studies.