My son has begun to lie fairly frequently over the past couple of months. He used to tell lies by making up stories that were fantastic and clearly not true. He has recently graduated to telling "bold face" lies. For example, when asked recently if he brushed his teeth, he calmly said "yes." My wife and I knew that he had not brushed his teeth, so we asked if he was sure. He calmly answered "yes" again. We then said that we were going to check if the brush was wet. His eyes got wide and he said "No! Don't do that!" We scolded him for this (verbally, no punishment was issued), but it doesn't seem to have helped.
I know that kids lie occasionally and it would not be realistic at all to expect that his lying would stop completely. However, it has gotten to a frequency and severity that is unacceptable lately. Can anyone recommend measures that my wife and I should take to abate this bad behavior?