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Neurolinguistic Evaluation

May 2003 (click here for printable version)

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Neurolinguistic Evaluation


The outer cortex of the human brain is divided into left and right hemispheres. When performing different activities, one hemisphere dominates over the other. In 80% of the population the left hemisphere is associated with creativity and assessment whereas the right hemisphere is associated with analytic thinking and factual recall. Furthermore, the direction in which a person breaks gaze (right or left) reflects the hemisphere of the brain being accessed for information. Because of the arrangement of neuropathways, breaking gaze to the left indicates that the right hemisphere of the brain is being accessed and breaking gaze to the right means the opposite.

This phenomenon can provide investigators insight on the truthfulness of a subject=s recall during an interview. Consider that a subject is asked, AWhere did you eat lunch yesterday?@ If the subject tells the truth he will break gaze to the left, indicating that factual information is being retrieved from the right hemisphere of the brain (for the majority of the population). If the subject breaks gaze to the right before answering this question (for the majority of the population) this indicates either fabrication or editing of information. In other words, the creative and assessment hemisphere of the brain is being accessed.

Establishing a Subject=s Norm

To properly use neurolinguistic evaluations during an interview, the investigator must first establish the subject=s normal direction of breaking gaze when recalling factual information. This can be accomplished at the outset of the interview by asking background questions that require long-term factual memory. Examples of these questions include, AWhere did you work prior to this job?, AWhat year were you married?@or, AWho was your previous supervisor?@ Notice that each of these questions has only one truthful response and the subject is unlikely to lie to the questions.

Questions requiring a possible judgment or assessment may offer misleading information with respect to establishing a subject=s normal direction of breaking gaze when recalling factual information. For example if a subject is asked, AHow long have you owned this vehicle?@ he may respond, AAbout three years.@ While the suspect is not likely to lie to this question, his answer involves an estimation (assessment) which may stimulate the creative hemisphere of the brain. A better question to ask is, AWhat is the year and make of your vehicle?@

There is no correlation as to which hemisphere of the brain stores factual information and being right or left handed. A left handed subject is just as likely to break gaze to the left when recalling factual information. Furthermore, brain dominance (being right or left brained) does not predict the direction a person will break gaze to recall factual information. The only way to determine a subject=s normal direction of breaking gaze when recalling factual information is to establish his own normal behavior.


Neurolinguistic Evaluations During an Interview (The following discussion assumes that the investigator has established that the subject=s normal break of gaze when recalling factual information is to the left)

At first blush, it would appear that neurolingustic evaluations would allow an investigator to perform almost as a human lie-detector. Unfortunately, it is not quite that simple. Consider the following dialogue where breaks of gaze prior to the subject=s answers are indicated by: ü (right) a (left) û (straight) and dots (...) indicate each second the subject delays his response.

I: ADid you steal that missing $2,000 deposit?@

S:ûANo I did not@

I: ADid you help make up the deposit?@

S: û ANo. The manager made it up by herself.@

I: AHave you made any large cash payments this week?@

S:a AOn Monday I paid my rent which was $800 but that was a check. So I didn=t really make any large cash payments.@

I: ADid you make any cash deposits into your checking account this week?@

S: ü ... AMy payroll checks are automatically deposited so I don=t generally make cash deposits.@

This subject is deceptive and yet a straight-forward analysis of his neurolinguistic evaluation does not seem to support this opinion. When the subject lied to the first question he maintained direct, eye to eye contact. When a deceptive suspect enters the interview prepared to lie about his involvement in a crime, often his eye contact will be direct to anticipated questions. He has already made the decision to lie and therefore does not have to access cognitive centers of his brain to make this decision. Astute investigators, however, would pick up on his non-contracted denial which indicates a possible rehearsed response. When asked if he helped make up the deposit, again his eye contact was maintained, but this time it was because he was confident in his truthful response. The question about making large cash payments resulted in a break of gaze to the left, indicating factual recall. However, his response contained the qualifying word Areally@. The fourth response reveals the most deceptive criteria. When asked about making cash deposits the subject breaks gaze to the right indicating either fabrication or editing. In addition, there is a three second delay and an evasive response, including the qualifying word Agenerally@. What happened in this case is the subject stole the $2000 and deposited it into his checking account to help make delinquent payments, including his rent.

As this example illustrates, when evaluating the direction in which a suspect breaks gaze, it is important to evaluate the behavior in the context of the question asked, the suspect=s anticipation of the question prior to the interview and to consider the behavior in conjunction with other verbal, paralinguistic or nonverbal behaviors. At the risk of over-simplification, the following guidelines can be offered for neurolinguistic evaluations (for 80% of the population):





Direct Eye Contact

Confidence, recent recall

Rehearsed, prepared response

Break Gaze to Left

Factual recall

Factual recall

Break Gaze to Right

Editing / Estimation


Our most effective use of neurolingustic evaluations has been when asking a suspect an unanticipated question that requires long-term memory. One example, shown at our three-day seminar, is of a young woman who claimed to have been abducted at knife point for several hours. She relates that her male abductor took her into a liquor store (a story she had previously told the police). Because her story was originally believed, the police never questioned her about the activities inside the liquor store. During our interview we asked whether the man brought the knife into the liquor store with him, whether or not he bought anything and whether or not he showed ID to the clerk. These were all unanticipated questions that require long term memory. Prior to each response she clearly breaks gaze to the right as she feebly attempts to fabricate a response.


Because it is based on scientific research and established physiological phenomenon, neurolinguistic evaluation sounds as though it would be a powerful tool in detecting deception. Unfortunately, because of the variables involved, neurolinguistic observations must be carefully evaluated. They can certainly increase an investigator=s confidence in a suspect=s truthfulness or deception. However like all behavior assessments, neurolinguistic evaluations must be considered in conjunction with other behaviors that occur during a suspect=s response and throughout the suspect=s interview.


For more information on evaluating a subject=s eye contact during an interview or interrogation, consider attending our three-day basic course on The Reid Technique of Interviewing and Interrogation.


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