4.2 Applying detecting deception research

You might already have realised that there are problems with applying an activity such as the detecting deception activity to a policing setting such as the investigation that you are following. These problems include the fact that the consequences to the people lying or telling the truth in the activity we created were quite minor. In psychological research, this is referred to as involving ‘low-stake’ lies. First, the people were only involved in the theft of a small sum of money. Additionally, in the scenario we presented you with, if they convinced the interviewer they weren’t lying when they were, they won a small reward, but the incentives for truth tellers were non-existent and there were no negative consequences for those people who lied and were caught by the interviewer. Obviously, it would have been unethical to impose any real punishment on the participants in this task.

This is very different to the situation facing Neale in the investigation you are following. If he is caught lying, the criminal justice implications would be incredibly serious and so these types of lies would be referred to as ‘high-stake’ lies. For example, if Neale has lied to the police – even if he isn’t involved in any way in this crime – he could be convicted of a public justice offence such as perverting the course of justice.

Some psychologists would argue that while cues to deception might be seen in high-stake lies, they might not be seen where the lies are much lower stake. That said, in 2011, Vrij and Mann carried out an interesting study to test this idea. They showed police officers clips of ‘pleaders’ (i.e. people who appeared on TV to plead with the public about the whereabouts of their missing relatives but who were subsequently found to have killed them). Surely these completely realistic high-stake lies would be detected? Unfortunately, not – they found an accuracy rate of just 50%.

Research on detecting deception has identified an important flaw in how many people try to spot lies, which is that they tend to rely on cues to deception that are not diagnostically useful. For example, they may focus on nonverbal behaviours such as eye gaze, which do not actually correlate with deceptive behaviour (Vrij and Mann, 2001).

Interestingly, though, research has shown that the person carrying out the interview is perhaps less well equipped to observe when someone is lying than someone who is just observing, just as you are able to when following this investigation. As the interviewer, DS Sund is mentally very busy during the interview. She will be trying to think about the questions she needs to ask as well as concentrating on what Neale is saying, meaning that she is under what psychologists would call ‘high cognitive load’. In their research, Buller, Strzyzewski and Hunsaker (1991) found that observers perform better than interviewers in lie-detection tasks, probably because they are less mentally busy.

There are areas of lie-detection research that have shown some promise. For example, Shaw et al. (2013) found that asking someone to recall something out of its normal temporal order (in other words the order in which things actually happened) meant that liars tended to provide less detail than truth tellers. This is likely to be because liars rehearse events in normal temporal order and unexpected questions from interviewers such as, ‘What happened just before that?’ mean that liars have to inhibit what really happened as well as retrieve imagined data. Having to do all that at the same time requires a high cognitive load meaning the person is only able to provide short answers with limited detail. Therefore, asking unexpected questions is one possible way to differentiate truths from lies.

In summary, there is a lot of evidence to suggest that people are not that effective at detecting deception from their observations of either verbal or nonverbal behaviour. It also doesn’t seem to make a difference if they are a police officer or not. For this reason police officers need to find evidence regarding whether or not people are lying, rather than just rely on their sense that someone might be.