In 2004 Bella DePaulo, a visiting professor at the University of California, Santa Barbara, who specializes in studying forms of human deception, asked college students and members of the community-at-large to keep a notebook to tally up the number of lies they told in one week. By the end of the experiment, DePaulo found that the students had lied at least once to 38 percent of the people they came into contact with, while the community-at-large had lied to 30 percent of those with whom they interacted.

Based on her research, DePaulo insists that we all fall into one of two categories of liars:

• Some of us are "self-centered liars"—we lie in order to make ourselves look better to others.
  
  
• The rest of us are "other-centered liars"—we lie in order to avoid hurting someone else's feelings.
  

The experiment also found that the proverbial "white lie" was more often told to strangers; deeper lies were reserved for those the liar loved most.

"In everyday life, people are often telling lies," says DePaulo. "[It's] not to get something concrete that they want, like more money, but for psychological reasons…

"Sometimes in our real lives, our valuing of honesty clashes with something else we also value, like wanting to be gracious or kind or compassionate."