Isn't this unexpected? When using fast event-related fMRI, the brain didn't have to work as hard to tell a lie. The test paradigm involved cards and a "bluff" - but test subjects were also told that they could keep $20 if they could fool the brain scanner.
fMRI scanners predicted liars with an accuracy of 78%. The results suggested that at least this sort of lying is a suppression of truth.
Lying is a normal developmental process, but it still doesn't fail to frustrate parents from time-to-time. Prosocial lying ("white lies") seems to start about the age o three, but self-protecting lies seem to really come into their own from ages 5 to 7.
One book we like on this subject is The First Honest Book About Lies*. At the bottom the cover in small print is, * You always have to read the asterisk. It talks about optical illusions, propaganda and advertising, white lies, and outright self-promoting lies. It's good for family discussions. After reading and reflecting on it, the kids have a more complex and realistic view of lying, and parents have told us they seem more thoughtful about developing their own standard of ethics.
Truth vs. Lie and fMRI
Lying: Encyclopedia of Children's Health
The Truth About Lying from Scholastic.com