4.1 Psychological theory and research on detecting deception
It would be very beneficial if there were ways in which we were able to detect deception within the criminal justice system. However, as you have learned in the detecting deception task you have just carried out, decades of psychological research suggests that when using our skills of observation, we are at around chance level at detecting deception. This means that we would perform just as well on deciding after each clip if the person is lying or telling the truth by tossing a coin! Also, importantly for our investigation, the research suggests that even in professional groups such as police officers, people are still at chance level when trying to detect deceit (Vrij and Mann, 2001).
We also learned in the deception task that people’s confidence and accuracy regarding their decisions about deception do not correlate (Vrij and Mann, 2001). This may be particularly problematic in the area of criminal justice, where people such as police officers may appear confident that they know someone is lying, but the research evidence shows that confidence doesn’t mean that they are actually accurate in the lie-detection decisions they make.
The psychological research suggests that when given a lie-detection task, most lay people tend to be better at detecting truths than lies – this is often referred to as a ‘truth bias’ (Levine, Park and McCornack, 1999). This human tendency to assume people are telling the truth makes sense a lot of the time. It would be pretty exhausting to always assume in our everyday interactions that someone might be lying to us, and so as a form of decision rule it probably saves us a lot of processing effort to hold a systematic bias that we are being told the truth.
Interestingly though, research has found that professional lie detectors (e.g. law enforcement officers or judges, for example) do not tend to hold this bias towards assuming people are telling the truth. Instead, they hold a lie bias (Bond and De Paulo, 2006) which, it has been suggested, may be caused by a generalised suspicion resulting from their professions (Masip et al., 2005).
In the next activity you can consider how your own responses might relate to these research findings.
Activity 7
By looking at your own results from the detecting deception activity you can work out whether or not you a) displayed a truth bias and 2) were better at judging lies or truths.
From your results, how many out of the eight did you think were telling the truth (regardless of whether or not you were correct)?
If you thought that more than half were telling the truth then you displayed a truth bias.
How many of the liars did you get correct (Person A, B, G and H) compared with the truth tellers (Person C, D, E and F)?
If you correctly spotted more of the truth tellers than the liars then you were better at detecting truths then lies – though note that simply by making more ‘truth’ decisions than ‘lie’ decisions’ (in other words displaying a truth bias) you will appear to be more accurate with truths than lies.