Excerpt from Telling Lies by Paul Ekman, PhD

What liars pay attention to

When lying, people usually do not monitor, control, and attempt to disguise all of their behavior; they probably couldn’t even if they wanted to. Instead, we tend to participate in verbal deceit, showing the most concern about choice of words. Liars censor what they say, carefully concealing messages they do not want to deliver, making detecting deception from words difficult. 

What we pay attention

Everyone learns in the process of growing up that people listen closely to what is said. Words receive such great attention because they are, obviously, the richest, most differentiated way to communicate. Similarly, we have learned that we will likely be held more accountable for our words than for the sound of our voice, facial expressions, or most body movements.

An angry expression or a harsh tone of voice can always be denied. The accuser can be put on the defensive: “You heard it that way but there was no anger in my voice.” It is much harder to deny having said any angry word. It stands there, easily repeated back, hard to disavow totally.