Mind
Do introverts have physically different brains?
More prefrontal grey matter
Do introverts have physically different brains?
Yes. MRI studies show introverts have greater grey matter volume in the prefrontal cortex — the region associated with planning, decision-making, and self-monitoring. Introverts also show higher baseline arousal in the brain's reward circuitry, which may explain why they need less external stimulation to feel content.
Source: Yagi et al. (2010), NeuroImage; Johnson et al. (1999) fMRI