What do we know about why we lie?

From telling your friend that you like their haircut when secretly you don’t, to walking along the street and pretending not to notice an acquaintance in the distance who you’d rather avoid, deception and lying is a well known trait. In this real life example, Jimmy Kimmel’s programme interviews people going to a music concert, many of whom pretend to know the bands that the interviewer is asking them about. The bands don’t exist, so the people interviewed are making it up. Why?


There may be justification for self-deception and lies. Looking at lying from the different perspectives of human science (psychology) and ethics, you could analyse what different explanations there might be for this.

The popular TV drama “Lie to Me”  is about a psychologist who claims to be able to read people’s facial expressions and tone of voice to determine whether or not they are lying. The actor Tim Roth plays Dr. Cal Lightman who is an expert in lie detection. Whilst this is an entertaining drama about his ability to spot liars in his professional and personal life, it raises questions about the reliability of his method. In TOK we might ask whether his interpretation of body language counts as a scientific approach? How far are his conclusions about human behavior based on reason, emotion, or language? If his judgments are a ‘hunch’ do they constitute reliable knowledge? If he claims that body language, facial expressions and tone of voice can reveal truth or lies what implications might this have?



To explore this further it is worth considering the “science” behind the series. It is based on the work of Paul Ekman, Ph.D. He is  an expert on facial expressions and a professor emeritus of psychology at the University of California San Francisco School of Medicine. For each episode he identifies the “science” behind it. His 15 books include the titles, “Telling Lies” and “Emotions Revealed.”

Consider these quotations from the trailers above. Rather than accept or reject them at face value, consider the evidence for them. Perhaps think of examples or counter examples for each of them.

“When you hide the truth your face reveals it.”

“The truth is written on all our faces.”

“Actions speak louder than words”

“Words lie; your face doesn’t.”

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