Fullam et al's aim was ‘to investigate the relationship between neural responses during deception and psychopathic personality traits’. ^{Reference Fullam, McKie and Dolan1} One of my main concerns is that what the authors referred to as ‘deception’ was not actually deception. The study participants were aware that the truth was known and they were being asked to ‘lie’ for the study. I do not believe this to be a good enough surrogate for deception.

For the purpose of the study, the word ‘lie’ was defined as ‘the intentional giving of a false response and awareness that the response is false rather than a mistake’. I believe this definition to be inadequate. The definition does not take into account that participants were ‘told’ to provide untrue answers or the fact that the true answers were known by the assessors. This situation is more comparable to a dramatic performance or acting rather than deception. A more appropriate definition of a lie would include the intent to deceive that is always present in a lie. These participants did not intend to deceive anyone with the ‘false’ answers, so they cannot be seen as lying.

Furthermore, the study adopts an approach that does not take into account the emotional and contextual elements involved in deception. The consequences of lying or not lying during the study were also incomparable to real life. This reduces the ecological validity of the study and makes the findings difficult to generalise.

The participants were also ‘required’ to make a motor response in order to select their answer. This adds further complexity to the analysis of the study results and further dents the ecological validity.

One of the main findings was that ‘mean response times (seconds) were significantly slower during the lie condition’. Although the stated P-value (0.024) shows a statistically significant difference, the actual difference of a tenth of a second (the difference between 2.66 and 2.56 seconds) only equates to about 4% delay. In clinical terms this does not appear to be significant.

The functional magnetic resonance imaging (fMRI) does provide exciting opportunities for research, but the overall utility of this study appears to be very limited; further research of a higher quality is required in this fascinating but complex field.

To overcome some of the problems with the methodology, the researchers would actually have to deceive the participants regarding the aims of such a study. The British Psychological Society provides extensive guidance regarding the use of deception in research (www.bps.org.uk/the-society/code-of-conduct/ethical-principles-for-conducting-research-with-human-participants.cfm).