Poor Man's Polygraph Part 4
The simple question, "Why should I believe you?" can detect deception.
Posted Dec 10, 2010
Poor Man's Polygraph Part 4
Why Should I Believe You?
The Poor Man's Polygraph consists of a series of techniques that increase the probability of detecting deception using verbal cues. The Poor Man's Polygraph provides deceptive indicators, not proof of deception. No one verbal cue indicates deception, but the probability of deception increases when clusters of deceptive indicators are present. The Poor Man's Polygraph provides non-threatening, techniques to test the veracity of others using the cluster method.
The Poor Man's Polygraph consists of the following techniques: Well..., Land of Is, Forced Response, Why should I believe you?, and Parallel Lie. The Poor Man's Polygraph will be presented in a five part series. Part 1 presented the Well... technique. Part 2 presented the Land of Is. Part 3 presented Forced Response. Part 4 will present Why Should I Believe You? The Poor Man's Polygraph can be found in its entirety in Psychological Narrative Analysis: A Professional Guide to Detect Deception in Oral and Written Communications.
When someone provides you with an answer to a question, simply ask them "Why should I believe you?" Honest people typically answer "Because I am telling the truth" or some derivation thereof. Truthful people simply convey information. They focus on accurately presenting facts. Conversely, liars try to convince people that what is being said is true. Their focus is not on accurately presenting facts, but rather, convincing listeners that the facts presented represent the truth. Since liars cannot rely on facts to establish their credibility, they tend to bolster their credibility to make their version of the facts appear believable.
When truthful people are asked the question, "Why should I believe you?" their natural response is "I'm telling the truth" or some derivation thereof, because to them there is no alternate response. The facts are the facts. The same question put to liars introduces a degree of doubt. When liars perceive their stories are not fully believed, they attempt to supply additional reasons why their story should be believed instead of letting the facts speak for themselves.
When people answer other than "Because I'm telling the truth" or some derivation thereof, tell them that their response did not answer the question and repeat the question, "Why should I believe you?". If they again do not respond with "Because I'm telling the truth or some derivation thereof," the probability of deception increases. The failure to correctly answer the question, "Why should I believe you?" is not conclusive proof of deception but, rather, one indicator of deception.
The nature of criminal interviews and interrogations allows investigators to apply the technique in a straight forward manner. For example,
INVESTIGATOR: Tim, did you steal the money?
TIM: No, I didn't steal the money.
INVESTIGATOR: Tim, I haven't known you for very long and you haven't known me for very long, so I don't know if you are telling me the truth or not. Believe it or not, people have lied to me in the past to get out of trouble so tell me, Why should I believe you?
TIM: Because I'm an honest person.
INVESTIGATOR: Tim, I didn't ask you if you were an honest person or not. I asked you, Why should I believe you? (pause) Why should I believe you?
TIM: I don't know.
INVESTIGATOR: Tim, if you can't give me one reason why I should believe you, then how do you expect me to believe you?
TIM: I don't really care if you believe me or not.
Tim failed twice to correctly answer the question, "Why should I believe you?" which increases the probability of deception. Additionally, Tim's response, "I don't really care if you believe me or not" is another deceptive indicator. Truthful people do care if they are believed or not and typically provide push back when their veracity is questioned. Truthful people rarely show indifference when they are not believed, especially when the stakes are high. Tim displayed a cluster of two deceptive indicators, which further increases the probability of deception.
Parents should apply the technique with more tack to avoid a direct confrontation with their kids. This technique is a more direct approach and discretion is advised. Consider the following exchange between a dad and his son.
DAD: There was $10 on my dresser this morning. It's no longer there. Did you take money from my dresser for any reason?
DAD: Son, I want to believe you. I do. But I'm having a hard time. Tell me. Why should I believe you?
SON: I'm not a thief.
DAD: I didn't ask you if you were a thief or not. I asked you why I should believe you. Why should I believe you?
SON: Because I didn't steal the money. I'm telling you the truth.
DAD: I know you are and I believe you.
In this exchange, Dad softened his presentation of the question, "Why should I believe you? The son responded that he was not a thief. This response did not answer the question, "Why should I believe you?" Dad gave his son a second chance by telling him that the question was not whether he was a thief or not but, rather "Why should I believe you?" This time the son answered, "Because I didn't steal the money. I'm telling you the truth," which indicates the son was telling the truth. Dad acknowledged that his son told the truth. The fact that the son correctly answered the question, "Why should I believe you" does not mean he told the truth, but it does decrease the probability of deception.
Parents should not restate the question more than one time. Repeating the question, "Why should I believe you?" too many times may cause your kids to think that you are badgering them and could damage your relationship with them, especially if they are telling the truth. Additionally, using this technique too many times may alert your child to this technique, thus making it less effective in the future. This and other verbal indicators or deception are detailed in Fibs to Facts: A Parental Guide to Effective Communication.