It's not so much that girls lie; rather, it's well documented people in general don't understand themselves all that well. Self-reports of internal motivations

It's not so much that girls lie; rather, it's well documented people in general don't understand themselves all that well. Self-reports of internal motivations are notoriously misleading. That's why research like this (or just common-sense observation of what people DO, rather than what they SAY) is useful.