Any seasoned manager knows it's unwise to accept what employees say at face value. The real test of their honesty is whether they deliver on their promises.
Think of your employees' stated promises as an iceberg. The words they use represent the part of the iceberg that floats above water. The far bigger part underwater is revealed indirectly.
When someone makes an important promise, watch as well as listen.
Does the speaker make eye contact or mumble while looking down? Does the person lean slightly closer to you or sway and lean away? Is he or she standing still and straight or fidgeting and slouching?
Pay special attention to voice tone, tempo and volume. People who intend to honor a promise typically adopt a sincere, enthusiastic tone. They speak slowly and emphatically, as if to signal that they treat what they're saying seriously. And they turn up the volume slightly to underscore every word.