Shy Or Outgoing? Blame It On Your Brain

A University of Iowa, Iowa City, study adds to growing evidence that being shy or outgoing may be all in your head. Investigators looking at cerebral blood flow and personality have found more conclusive signs of different brain activity in introverts and extroverts. Debra L. Johnson, assistant research scientist in psychology, indicates that "We found more evidence that people might be shy or outgoing because of the way their brains are structured, not because of experiences they've had."

The researchers examined 18 healthy individuals utilizing positron emission tomography (PET) scans, which can generate a high-resolution image of the entire head. The scans revealed that introverts have more activity in the frontal lobes of the brain and anterior, or front, thalamus. These areas are activated when a person's brain takes on internal processing such as remembering, problem-solving, and planning. Extroverts exhibit more activity in the anterior cingulate gyrus, temporal lobes, and posterior thalamus. These areas are typically thought to be more involved in sensory processing such as listening, watching, or driving.

The differences in cognitive style and sensory-processing relate to the qualities associated with introversion and extroversion. True introverts are quiet, inwardly focused, and reclusive. Extroverts are gregarious, socially active, and sensation seeking. "Introverts get more of their stimulation internally, whereas extroverts seek outside sources," Johnson explains. "Extremely introverted and extroverted personalities are two ends of a continuum, with most people falling somewhere in between. The implication is that one personality trait--introversion or extroversion--isn't right or wrong. These variations in brain activity suggest that a lot of our individual differences have an underlying biological cause."

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