Lies, Damned Lies, and the N200
Daniel
+
Comstock ,
+
Davis ,
Brettina
Kaitlyn
Adrienne
Paul
+
Michael P.W. Donnelly, PhD* & Desiree Budd, PhD
+University
+
Olson ,
+
Sulma ,
+
Krause ,
Lindsay
+
Domagala ,
of Wisconsin-Stout & *Sulcus Scientific Consulting, Menomonie, WI
Background
Method
Can lies be detected by measuring physiological activity?
Decades of work on this question have failed to uncover a
physiological signal that unambiguously indicates deception. Our
study explores this question from a novel perspective.
• The oldest lie detection procedure, the Control Question Test
(CQT), involves an interrogator that asks a suspect yes/no
questions about a crime while measuring peripheral physiology,
in an attempt to detect arousal due to anxiety that should
accompany lying.
• A newer procedure, the Guilty Knowledge Test (GKT), attempts
to detect physiological neural activity that indicates familiarity
with information only a guilty person would know.
• In at least one variation of the GKT, researchers have claimed
that the P300 Event-Related Potential can be used to
unambiguously identify such familiarity, although this claim
remains controversial.
Ten subjects were given one or two Pokémon cards and were then interrogated
by an unseen interviewer as to which card(s) they had in their possession. They
were instructed to respond truthfully about one or more of the cards, and
deceptively about another card while we measured their brain activity using an
EGI 128 channel EEG System . In one condition, they attempted to deny having a
card, which they did in fact possess (False Denial). In another condition, they
attempted to confirm having a card, which they did not in fact possess
(False Affirmation).
Results
Topographic voltage map of EEG activity (µV) by condition at 100ms, 130ms, 190ms, and 310ms post stimulus.
µV
The Current Study
Consider a situation in which a person is interrogated, and their
answers are limited to YES or NO. In this setup, there are two
ways to tell the truth, and two ways to lie:
TRUE ANSWER
SUBJECT
RESPONSE
YES
NO
“YES”
True
Affirmation
False
Affirmation
“NO”
False Denial
True Denial
Our hypothesis is based on two assumptions:
1.The brain has distinct mechanisms for arriving at affirmative
and denial responses;
2.Generating a deceptive response requires that the brain
inhibit an automatic (truthful) response: the initial response
will be automatically truthful, followed by a response conflict
signal, followed by resolution of the conflict when the motor
command is programmed.
Conclusions
• False denials and false affirmations are processed differently after the initial sensory response. At 130 ms, the
neural response is associated with the truth about whether or not the card in the possession of the subject.
Specifically, True Affirmation is similar to False Denial and True Denial is similar to False Affirmation.
• By 200 ms, neural activity is associated with whether or not a lie is being told, as well as the type of lie.
Truthful responses show similar activation. Untruthful responses show increased parietofrontal involvement
similar to that found in fMRI deception studies. Specifically, they show increased activation related to the
right superior frontal gyrus and the left premotor cortex compared to the truthful conditions. Additionally, the
increased frontal activity in the False Denial condition compared to the False Affirmation conditions suggests
additional resources are needed to suppress the truthful response for lies of denial. Thus, considering the
N200 response in conjunction with P300 may enhance ability to detect lies using EEG.
Acknowledgements: We would also like to thank Jimmy Vance,
Lauren Strohm, and Sarah Jung for their help on this project.
Partially Funded by DUE: 1020906
For more information contact buddd@uwstout.edu