Liar liar! The neuroscience of sex differences in deception

Posted on December 10, 2012

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If you have seen the 2010 film Salt starring Angelina Jolie, you may be familiar with a scene that takes place in an interrogation room, in which an informant accuses Jolie’s CIA agent character of being a Russian spy. The other CIA agents watching this exchange from behind a two way mirror don’t seem convinced, that is until a voice coming from one of their computers suddenly announces the word “truthful”. It cuts to a woman sitting at said computer, a brain scan displayed on the monitor, “So far the fMRI scan registers truthful on everything he’s said” she declares.

Salt1

The world’s first completely invisible fMRI machine

This is clearly an improbable and exaggerated idea based on a scientific method (especially because there doesn’t actually appear to be an fMRI machine anywhere near the man being questioned). Nevertheless it does point out a growing fixation on the idea that brain imaging, especially fMRI, is a super tool which can tell us what a person is truly thinking (research has found that perceived credibility of neuroscience articles was increased simply due to the presence of brain images, although this has been debated).

Whilst the reality of what is actually achievable using fMRI may not be as thrilling, there does seem to be a real interest in what happens in our brains when we try and deceive another person. For example, research has looked at activations in simple lie vs. truth paradigms (e.g Phan et al., 2005) and also when telling different types of lies (e.g Ganis et al., 2003).

A recent study by Marchewka and colleagues (2012) carried out an fMRI study looking at a previously under-studied feature of deception. Specifically, whether neural differences between men and women exist when it comes to lying.

Clinton

We know his pants were on fire, but what was happening in his brain at this moment?

Methods

The central method of the study consisted of instructing 15 female participants and 14 male participants to either lie or tell the truth in response to 120 questions (for example, “Do you Speak French?” and “Do you have a sister?”), all whilst inside an fMRI scanner. The questions were devised from information that the participants had provided the previous day regarding personal information and general knowledge. The fMRI data allowed the researchers to see which areas of the brain were activated whilst the truth/lie responses were being given.

An extra element to the research was introduced owing  to the concern that participants would not have any real incentive to want to lie, participants were told that ‘lie experts’ were assessing them and that those most adept at lying would be rewarded with money . This was not really the case however; instead, accuracy of answer and the time taken to respond were the real behavioural measures of deception performance.

In a secondary aspect of the study, the participants completed a questionnaire relating to their gender identity.  The researchers wanted to check whether socialisation of gender roles (e.g. men socialised to exaggerate risky, individualistic behaviour and women socialised to conceal behaviour that may upset others) played a part if differences arose (as opposed to differences purely being associated with biology).

Results

The behavioural results revealed no statistical difference between men and women on the deception task. Essentially, the male and female participants were as good as each other when it came to the act of lying.There was also no association with gender identity in any of the results, suggesting that socialisation processes did not play a role.

A number of brain areas were activated in both men and women when lying. Interestingly, one significant difference did reveal itself within the fMRI data. Specifically, a higher blood oxygen level dependant (BOLD) response was found in the left middle frontal gyrus (MFG) of men when lying about personal information in comparison to women.

MFG1

Greater levels of activation in the left MFG of males in comparison to females.

So what does this actually mean? The researchers outlined previous research in which the left MFG has been linked to inhibition and the selection of information (i.e. the lie) despite the presence of conflicting information (i.e. the truth). Based on the reasoning ‘more activation = a more cognitively demanding task’, the researchers suggested that the finding could point to men using a greater amount of neural effort for these processes when lying about personal information in comparison to women. So could it really be that men find it harder to lie about themselves?

The finding is an interesting one but there is the question of whether more activation truly equates to any increased effort. There have been criticisms of fMRI data, for example we cannot always be sure what the signal is actually representing (Logothetis, 2008) and alternative interpretations of activations are always possible because brain areas are not exclusively activated for only one process or task (Aue, Levelle and Cacioppo , 2009). Indeed, it is hard to know in this research what the higher level of activation in the left MFG really means. However, this is not to say that fMRI is not a useful tool within neuroscience research, especially when trying to study processes that would otherwise be unknown if we solely relied on behavioural and verbal data.

There are also some possible issues with the ecological validity of the study (apart from the obvious point that telling a lie in a machine which is essentially a giant, noisy magnet is not necessarily indicative of a real life situation) which the researchers themselves acknowledge:

The participants were instructed to make deceptive responses, which may not be equivalent to deception during real life conditions” (p. 8).

The removal of any sort of wilful intention to lie is problematic for this research and simply put, being told to lie is not the same as wanting to lie. The instruction to lie eliminates a number of aspects that are central to lying, such as guilt/internal conflict and damaging consequences for the participant if they do not achieve deception. Additionally, other than financial incentive, there was no real personal or emotional gain for the participant in successfully lying. So is deception truly being measured here? Sip and colleagues (2008) think not, suggesting that methodology such as this actually examines executive function processes (associated with the act of deceiving) rather than deception itself. They stated that it is:

“Not simply a matter of inadequate contextualisation but goes to the heart of the act, eliminating its status as deceptive” (p. 48).

So the methodological issues in this research certainly raise the question of what is truly being measured, and a take home message from this may be to view findings such as this with a certain amount of caution. However, the central research question is undeniably an interesting one. Investigating gender differences of everyday phenomena will always be appealing because it feeds straight in to our curiosity of why men and women have been proverbially known to ‘live on different planets’. However, we still have a way to go in understanding such differences in terms of neural processes.

References

Aue, T., Lavelle, L.A. & Cacioppo, J.T. (2009). Great expectations: What can fMRI research tell us about psychological phenomena? International Journal of Psychophysiology, 73, 10-16.

Ganis, G., Kosslyn, S.M., Stose, S., Thompson, W.L. & Yurgelun-Todd, D.A. (2003). Neural correlates of different types of deception: An fMRI investigationCerebral Cortex, 13(8), 830-863.

Logothetis, N.K. (2008). What we can do and what we cannot do with fMRI. Nature, 453, 869-878.

Marchewka, A., Jednorog, K., Falkeiwicz, M., Szeszkowski, W., Grabowska, A. & Szatkowska, I. (2012). Sex, lies and fMRI – Gender differences in the neural basis of deception. PLOS one, 7(8), 1-11.

Phan,  K.L., Magalhaes, A., Ziemlewicz, T.J., Fitzgerald, D.A., Green, C. & Smith, W. (2005). Neural correlates of telling lies : A functional magnetic resonance imaging study at 4 Tesla. Academic Radiology, 12(2), 164-172.

Sip, K.E., Roepstorff, A., McGregor, W. & Frith, C.D. (2008). Detecting deception: the scope and limits. Trends in Cognitive Sciences, 12(2), 48-53.

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