Lies and cognition: how do we tell lies and can we detect them?

The present thesis focuses on two main areas of deception research. The first of these examines the cognitive processes involved in telling a lie and the second examines human ability to detect deception. Since deception research has historically lacked a solid theoretical basis, this work extends previous research by providing a greater theoretical understanding of both the processes involved in telling lies, and also those involved in successfully discriminating truthful messages from deceptive ones. In the first section, a simple response time paradigm is used to examine how cognitive processes differ when individuals lie compared to when they tell the truth. This paradigm is manipulated to examine the effect of a variety of different factors on potential processing differences, such as the number of lie response options available and the order of lie and truth responses. Overall, the contention that telling a lie is more cognitively demanding than telling the truth was supported. This additional cognitive load should aid in the discrimination of false and truthful messages by human observers. The second section of the thesis therefore examines individual differences in human ability to detect deception. A number of individual difference variables were examined, including extraversion and autism spectrum characteristics, allowing for the exploration of the potential relationship of these measures with both deception detection accuracy and degree of truth bias when judging the messages of individuals from different cultural backgrounds. Overall, reliable individual differences in ability levels were not found. A positive relationship between extraversion and degree of truth bias, however, was demonstrated when participants judged individuals from the same cultural background as themselves compared to a different cultural background