Whom Should You Trust?

When should you trust someone? Is the answer more nuanced than "Trust Allah but tie your camel tight?"

In determining whom to trust and in what circumstances, you might want to keep tabs on at least the key people in your life:

• How often does that person say something not in his self-interest, even though he wouldn't be caught? For example, "Mary, this wasn't your fault. The data I gave you was incorrect." The greater the price the person pays for his inexpedient honesty, the more you can trust him the next time.
  

• How accurate have his promises been? For example, "I'll call you tomorrow," "I'll have it done by Monday," or "I'll get you a raise soon." It doesn't really matter if the person miscalculated or is lying. What counts as you decide whether to trust her next promise is: How well has she kept previous promises? How accurate have her predictions been--whether on the company's future, the quality of a product, whether she really will stay with you even if you lost your job, etc?
  

Alas, as mutual fund prospectuses always tell us, past results don't perfectly predict future performance but we can up our odds by becoming a human lie detector. Law enforcement interrogators have learned techniques to assess the veracity of a person's statements:

• Watch the eyes and forehead. Most good liars and exaggerators have long learned to control the obvious signs of lying: pursed lips, crossed arms, etc. It's harder to control the eyes and forehead. So watch a person's eyes when he's saying something that's unquestionably factual. Then, when he's saying the in-question statement, do his eyes train somewhere else? Also look for a discrepancy between the mouth and the eyes, for example, smiling but with a tense-looking forehead and eyes.

• Look for changes in a person's behavior. Beware if, when making a potentially dishonest or incorrect statement, a person's voice or body language changes. Examples: becoming more monotonic and slow-paced, losing eye contact, turning away or crossing their legs, ceasing use of hands while talking, breathing more quickly and shallowly, stiffening, starting a nervous mannerism such as foot wiggling or face touching. If you suspect someone's lying, change the conversation to something clearly factual and see if she reverts to her previous interaction style and seems glad to change the topic.

• Quick stop-start emotions. Real emotions often build and fade slowly. Phony ones often get turned on and off quickly.

• Re-ask. Later in the conversation, ask the same question. Does the person give the same answer or are some details changed?

Of course, none of this is foolproof. For example, some people don't show signs of lying because they're calm by nature, have an autistic-spectrum disorder, and/or are sociopathic. Sometimes, a person's exhibiting signs of lying merely reflect nervousness in talking about a difficult topic.

Just because you catch someone lying doesn't mean you should confront him. For example, I tend to remain silent when a face-saving lie is unlikely to cost me much now and is unlikely to encourage bigger, more costly lies in the future.

Of course, we live in a world filled with lies and inaccuracies but excessive vigilance can cost us too much: It can make us exude suspiciousness and cynicism. It may even preclude us from close relationships. Perhaps moderate trustworthiness is all we can reasonably expect.

Maybe the best balance can be struck by my father's advice: respect but suspect. I'd add, "and balance justice with mercy."