So in the drama you have been watching, one of the detectives became convinced that a
witness was being deceptive, and based on this hunch sought a confession from the witness.
It is sound to rely on such hunches? Can we really tell if people are lying to us?
And does this mean that one of the reasons why police seek confessions using stronger
interview strategies is because they 'know' who is guilty?
Well, some researchers, such as Roesch, Zapf and Hart in 2010 argue that this might be
part of the issue.
If I thought someone was innocent or knew nothing I would release them immediately.
In the following video, you will see a witness make some statements. When you watch this
video, I want you to try and decide whether the person is telling the truth or not.
I’m not quite sure why I’m here.
You ran from the murder scene, Scott, that's why you’re here.
Now hang on mate…
No you hang on, mate! There’s a dead girl lying on a cold bit of steel refrigerator and it’s
my job to figure out who the h**l put her there. Now sit back down!
You can’t prove I took that bag. Maybe somebody nicked it.
I'm guessing that the majority of people will think that the witness was being deceptive.
How can you tell whether someone is telling the truth or not?
One of the things that people think you should pay attention to when trying to detect a lie
is non-verbal behaviour.
The idea is that when verbal and non-verbal messages do not match, the non-verbal behaviour
is the better indicator of the truth because it is harder to control.
Why is it so hard to control non-verbal behaviour?
Well, there are relatively automatic links between emotions and non-verbal behaviours.
So if you experience the emotion of fear for example, you might then display a particular
facial expression or body movement without conscious control of those expressions and
movements.
The other issue is that people are relatively unaware of what "normal" non-verbal behaviour
is, and so are not well practiced at controlling nonverbal behaviour. So it is harder to make
your non-verbal behaviour match your relatively controlled verbal behaviour when you are actively
trying to look like you are not being deceptive.
This leads us to two important questions:
Are there systematic differences in non-verbal behaviours between liars and truth tellers?
And, are observers aware of these cues, and also, perhaps most importantly, are observers
able to detect deception using these cues?
The answer to these questions needs to be 'yes' for observers to be able to detect deception
from non-verbal behaviour.
There are basically three theoretical frameworks for answering these questions.
The first is the emotional approach, proposed by Paul Ekman in 1985. This perspective suggests
that being deceptive causes certain physiological reactions such as high blood pressure and
increased heart rate. These reactions are the result of heightened arousal associated
with guilt, fear or perhaps excitement. It is also this arousal which is thought to effect
non-verbal behaviour.
The second approach is Burgoon and colleagues' cognitive approach.
According to this perspective, being deceptive is a cognitively complex task, and because
of the cognitive load associated with deception, body language gets neglected. As a result,
there is a reduction in the overall amount of movement, slower speech, and more pauses
in speech.
The final approach is DePaulo's 'attempted control approach', or the
self-presentation perspective as it’s sometimes called. It argues that deceivers will try
to control their behaviour, but because they are not very practised at being deceptive,
their behaviour appears more rigid and inhibited.
The interesting thing here is that these three approaches all actually predict different,
and sometimes contradictory, behaviours as markers of deception.
The emotional approach predicts that increased movements will be associated with being deceptive.
The emotional and cognitive approaches predict an increase in speech
disturbances as being associated with deception. Whereas the attempted control approach suggests
that there should be a reduction in movement.
So what does the research say actually happens when people are being deceptive?
Depending on the study, deception is associated with more speech disturbances and slower speech
rate, as in DePaulo et al.'s 1989 study, or fewer speech disturbances and faster speech
rate as in Vrij's 1995 study.
As it turns out, speech rate and number of disturbances depends on the type of lie that
is being told. Fabrication of false information, rather than just concealing the truth, is actually
harder to do and so leads to more speech disturbances and slower speech rate.
Voice pitch, on the other hand, does seem to be relatively uniformly associated with
deception.
What about non-verbal behaviours like body movements?
Vrij's 1995 study tells us that when people are being deceptive, we tend to see less movement
of hands, arms, feet, and legs. This study also tells us that gaze, smiling,
and shifting position are not really reliable indicators of deception. And so the old adage
about looking up and to the left as a marker of deception is probably not supported by
the results of systematic research.
Is that all that all that is associated with deception?
Well some people argue that due to the limits of what you can do in an experiment in the
laboratory, we can't understand the full range of behaviours associated with deception. For
example, for ethical reasons it is difficult to create situations in the laboratory that
have high stakes, or important consequences, for participants.
It can also be difficult to create situations where participants have high levels of motivation
to get away with a lie, or high levels of motivation to detect a lie as they might in
real life.
What we know from other types of research, like observational studies, however, is that
high stakes for getting away with a lie do not tend to produce more nervous behaviour.
This can be seen in studies by Davis & Hadik, in 1995 and Vrij and colleagues in 1996. Some
of that research actually showed that Saddam Hussein decreased his movements when attempting
to get away with a lie.
Highly motivated liars do behave in different ways however. They show fewer body movements,
and slower speech rate, higher voice pitch, and more speech disturbances.
Finally, we also know that people who have had time to plan their lie behave differently.
Zuckerman and Driver's 1985 study showed that planning was associated with fewer arm and
head movements, shorter response latencies, and faster speech rate.
So the next question is whether observers can actually tell when others are lying or
not by paying attention to these non-verbal cues?
“With about three-quarters of people I can tell [if they’re lying] pretty much instantaneously.”
“… a hand comes near the mouth, or a swallow before an answer… is eye contact suddenly
different? Does the person repeatedly look off to the left as she searches for true answers
to questions, then suddenly look off to the right… when she gives one particular answer?”
So to come back to our question, can people detect lies?
Although there are some exceptions, which we will talk about soon, the answer is generally
that people are no better than chance at detecting deception.
Bond and DePaulo reported an average lie-detection accuracy for lay persons of 54% in their 2006
study.
It's not just lay people though. People who work in law enforcement, such as police officers
and customs officials, also perform at chance levels, as shown in research by Kraut & Poe
in 1980. There are some exceptions to this however, such as secret service agents and
some members of the intelligence community, as Ekman & O'Sullivan, observed in 1991. But
the general rule holds that people are no better than chance.
Now why is that? Well let's start by asking the question in a slightly different way.
What non-verbal behaviours do people think are linked with being deceptive? Vrij and
Semin in 1996 asked professional lie detectors, students, and prisoners this very question.
They found that prisoners were significantly better at identifying the cues associated
with deception (32%) compared to the other two groups of participants.
Now what is one reason for this? Well, professional lie detectors, such as police, might not perform
better than non-professional lie detectors because they don't get very good quality feedback
on whether someone is actually being deceptive or not. In investigations, it can be very
difficult to know with absolute certainty, what exactly went on. And as we've heard,
even when we have a confession to a crime, or an eyewitness identification or account
of events, these may be misleading for a whole range of reasons.
It's also possible that prisoners are particularly good at lie detection because it’s more
essential for them to do this well. It can literally mean the difference between life
and death.
Now lack of training might also contribute to the relatively poor deception detection
performance for some groups.
Porter, Woodworth and Birt in 2000 looked that the role of training. They found that
training, practice and feedback in detecting the nonverbal indicators of deception all
actually improved accuracy.
Mann, Vrij and Bull in 2004 also showed that more experienced officers performed better
than less experienced officers, and they also at better than chance levels. Experienced officers
were able to detect deception with an accuracy of 65%.
So in sum, people in general are not very good at detecting deception, and with a few
very special exceptions, they are really no better than chance - you may as well be guessing!
Interesting, even though people are generally not very good at detecting deception, people
are confident in their ability to detect lies as research by Vrij in 1993 shows. Unfortunately
the correlation between confidence in ability to detect lies and accuracy in detecting lies
is not very strong.
Why is this?
Well observers generally think that deception is associated with increased speech disturbances,
high pitched voice, longer latency during speech, and looking away which is also called gaze aversion.
And they also think it is associated with increased body movements.
Now from the start of this presentation, you will know that voice pitch is the only one
of those behaviours that is reliably related to deception. Speech disturbances and latency
periods are related to deception, but the nature of that relationship changes with the
different types of lies that can be told. And in fact, you also know that it is actually
decreased body movements that are associated with deception.
So why do people think that these things are associated with being deceptive when they might not be? Probably
because they are all markers of being nervous, and as Knapp and colleagues showed in 1974,
people assume that liars will actually be nervous.
Essentially the problem is that people have a stereotype about what it means to look deceptive,
and parts of that stereotype are accurate (as for voice pitch) and parts of that stereotype
are inaccurate (the other cues that we talked about).
Interestingly, some of our research that was published in 2013
actually suggests that people are most influenced by the parts of the stereotype
that are inaccurate, and they largely ignore the parts of the stereotype that are accurate.
Now this makes it really hard for people to accurately detect deception!
Having been rather pessimistic about observers' ability to detect lies, there are a few ways
that people can be more accurate in this task.
We've already heard how training in deception detection, and just generally having more
experience at it, helps to improve accuracy rates.
Ekman and O'Sullivan argue that if you train people to specifically pay attention to micro
momentary expressions of the face, you can increase their ability to detect lies as well
Slepian and colleagues 2013 study of poker players' ability to detect deception, suggest
that cues unrelated to the face might be more useful. They found that observers were more
accurate at identifying the quality of other poker players' hands by paying attention to
the hand movements when placing bets rather than the players' faces and upper bodies.
So perhaps we need to stop focusing on the eyes and other facial features.
Perhaps consistent with this, Porter and Brinke in 2010 argue that paying attention to multiple
cues, rather than just a single cue, can improve lie detection ability.
On the other hand, Reinhard and colleagues 2013 study suggested that observers should
avoid consciously trying to attend to cues at all, and rely instead on unconscious processing
of multiple cues. In their study, unconscious decision makers, that is, people who were
kept from actively thinking deliberatively about detecting deception, actually performed
the best and at better than chance levels.
So perhaps telling people to actively pay close attention to verbal and non-verbal behaviour
or demeanour is not necessarily the best way to detect deception. This is a point
made originally by Meissner and Kassin in 2004.
Apart from these avenues for potentially improving deception detection, is there some other way
we might be more accurate that doesn't rely on perceivers’ own perceptions of nonverbal
behaviours? What about lie detection machines? We will talk about the polygraph and other
such machines in the next presentation.