Many sources support the premise that lying is
cognitively demanding. First, in police interviews
with real-life suspects, lies are accompanied by
increased pauses, decreased blinking, and decreased
hand/finger movements, all of which are signs of cog-
nitive load. Second, police officers who saw video-
tapes of suspect interviews reported that the suspects
appeared to be thinking harder when they lied than
when they told the truth. Third, participants in mock-
suspect experiments directly assessed their own cog-
nitive load during interviews and reported that lying is
more cognitively demanding than truth telling. Finally,
deceiving is associated with activating executive,
“higher” brain centers (such as the prefrontal cortex),
which are typically activated when high cognitive
load is experienced.
By using protocols that introduce additional cogni-
tive load, investigators can exploit liars’ higher cogni-
tive demand to facilitate discrimination between liars
and truth tellers. For example, interviewees could be
asked to recall their stories in reverse order. This task
is cognitively more demanding than recalling a story
in chronological order. Liars, whose cognitive resources
are depleted by the more demanding act of lying, find
reverse order recall more debilitating than do truth
tellers because liars have fewer cognitive resources
left over than truth tellers. Indeed, research has
demonstrated that liars and truth tellers differ more
from each other in terms of displaying signs of cogni-
tive load when they recall their stories in reverse order
than in chronological order. The occurrence of more
noticeable differences between liars and truth tellers
should facilitate lie detection. Indeed, investigators
were more accurate in discriminating between liars
and truth tellers when the interviewees told their sto-
ries in reverse order than in chronological order.
An alternative technique to induce additional cog-
nitive load is to require interviewees to perform a con-
current secondary task (time-sharing) while being
interviewed. Again, liars, whose cognitive resources
are already partially depleted by the act of lying, find
this additional, concurrent task particularly debilitat-
ing. An experiment revealed that this showed up as
poorer performance on the primary task (e.g., provid-
ing a statement during the interview) and also on the
secondary task (e.g., determining whether each figure
presented on a screen was similar to the target figure
presented earlier).
Investigators sometimes have evidence available,
such as fingerprints and closed-circuit TV footage,that may link a suspect to a crime. They can then pre-
sent this incriminating evidence against a suspect in
a strategic fashion to increase cognitive load by lim-
iting the number of acceptable explanations suspects
can offer to account for the current situation.
Suppose that the suspect’s car was noticed near the
crime scene just after the crime had taken place but
that the suspect did not refer to the car in his or her
alibi. After being confronted with this piece of evi-
dence, the suspect may reply that he or she had sim-
ply failed to mention previously that he or she had
used the car on that particular day, thereby adapting
his or her story to match the evidence. However, sup-
pose that the police officer does not reveal at this
stage that the car was noticed near the crime scene
but asks some questions about the car instead (e.g.,
“Did you use your car that day?”). When confronted
with the evidence after these questions, the suspect
has fewer opportunities to provide acceptable solu-
tions if he or she has already told the interviewer that
he or she did not use the car on that particular day.
The number of acceptable solutions would be
reduced even further if the suspect indicated that he
or she did not lend the car to anyone else and that
nobody else had the car keys.
In sum, investigators using cognitively based inter-
view protocols increase their ability to discriminate
between liars and truth tellers by making the interview
situation more taxing for interviewees.Aldert Vrij, Ronald Fisher,
Samantha Mann, and Sharon LealSee alsoDetection of Deception: Magnetic Resonance
Imaging (MRI); Detection of Deception: Use of Evidence
in; Detection of Deception in High-Stakes LiarsFurther Readings
Hartwig, M., Granhag, P. A., Strömwall, L., & Kronkvist, O.
(2006). Strategic use of evidence during police
interrogations: When training to detect deception works.
Law and Human Behavior.
Vrij, A., Fisher, R., Mann, S., & Leal, S. (2006). Detecting
deception by manipulating cognitive load. Trends in
Cognitive Sciences, 10,141–142.
Vrij, A., Fisher, R., Mann, S., & Leal, S. (in press).
Increasing cognitive load in interviews to detect deceit
[Invited chapter]. In B. Milne, S. Savage, & T. Williamson
(Ed.),International developments in investigative
interviewing. Uffculme, UK: Willan.196 ———Detection of Deception: Cognitive LoadD-Cutler (Encyc)-45463.qxd 11/18/2007 12:41 PM Page 196