interrogation manuals, which typically emphasize
nonverbal cues to deception, and contradicts pre-
sumed experts’ and lay people’s beliefs about what
gives a liar away as well.
The results presented so far are at the most general
level—across all available studies without taking
into account differences in the experimental designs.
There are, however, a few presumably moderating
factors that have been studied often enough to allow
for interesting conclusions; three of these are dis-
cussed below.Transgressions
An important factor, and most relevant to the forensic
context, is the distinction between lies that are about
transgressions and those that are not. Lies about trans-
gressions are told to hide and/or deny acts such as
cheating, stealing, and committing other crimes, small
and large. In other studies, participants, for example,
pretended to experience another emotion that they did
not in fact experience or lied about their opinions. The
question is whether differences between liars’ and
truth tellers’ nonverbal behavior emerge when they are
interviewed about transgressions they have or have
not committed.
The literature describing the lies that were not
about transgressions shows only one behavior that
separates the liars from the truth-tellers, and that is
fidgeting.When participants were talking about their
likes or dislikes, their opinions and emotions, or any-
thing else that did not involve a bad behavior, they fid-
geted more when lying than when telling the truth.
The cues to lies about transgressions are more impor-
tant in legal contexts. People lying about transgres-
sions look more nervousthan do truth tellers; they also
blink moreand have a faster speech rate.Additionally,
they are more inhibited than truth tellers in the sense
that they move their feet and legsless often.Motivation
In many studies, the liars did not have any special
motivation to tell a convincing lie. Many simply par-
ticipated as part of a study, with no special rewards for
succeeding or punishments for failing. It is of impor-
tance to separate those studies in which participants
had some special motivation to do well and those in
which they did not. The question is this: If people are
motivated to get away with their lies, will that show
up in the form of fewer cues to deception because theyare trying harder to tell a good lie or will their lies
become more obvious as the stakes are raised?
Research has shown that when participants had no
special incentives, there were no obvious nonverbal
cues to deception. When people do not have that much
invested in their lies, others will have a very hard time
knowing when they are lying. However, when liars do
care about getting away with their lies, then several
behaviors may betray them. It is only when partici-
pants are motivated to do well that they speak in a
higher pitchwhen lying than when telling the truth.
Although liars also seem tenserthan truth tellers
regardless of motivation, the difference is pronounced
for those who are highly motivated to get away with
their lies. In the previous section, in which results
were summarized for all studies, there were no differ-
ences whatsoever in how often liars looked at the
other person and how often truth tellers did. But when
participants are motivated to do well, then one stereo-
type about liars becomes a reality: They make less eye
contactthan truth tellers do. There was also some evi-
dence, under high motivational conditions, that liars
made fewer foot and leg movementsthan truth tellers.Preparation
Sometimes suspects know beforehand that they are
going to be interviewed, which gives them a chance to
prepare their answers. Presumably, liars should man-
age to appear more like truth tellers when they can
plan their answers in advance than when they cannot.
The available research indicates that when having
time to plan, liars have shorter response latency than
truth tellers. When there is no time to prepare, the
opposite pattern is found. There is also some evidence
that liars show shorter message durationthan truth
tellers when they have time to prepare their responses.Limitations and Conclusions
Although researchers have in some studies tried to
raise the motivation of and the stakes for the lying
participants, the question still remains how the results
from laboratory-based studies reflect what may hap-
pen in real-life high-stakes situations such as police
interviews.
In a few studies, the behavior of real-life suspects,
interviewed about serious crimes such as murder,
rape, and arson and facing long prison sentences if
found guilty, has been examined. Results revealed that
these suspects did not show the nervous behaviors202 ———Detection of Deception: Nonverbal CuesD-Cutler (Encyc)-45463.qxd 11/18/2007 12:41 PM Page 202