Pathological lying may stem from an unusual imbalance of brain matter, say scientists at the University of Southern California. Working with senior investigators, doctoral student Yaling Yang scanned the brains of 12 self-described pathological liars as well as other volunteers who had no history of deception. Yang was surprised to find that the liars’ brains had 22 percent more white matter in the prefrontal regions that govern decision making and judgment. So-called white matter makes up the wiring among neurons, which are sometimes collectively called gray matter.