while some children are like dandelions and can thrive in any kind of environment, not all are quite so resilient. Adverse environments can be especially damaging to “high-reactive” children

Cain wraps up this chapter by sharing her experience of joining a public-speaking support group that used exposure therapy and desensitization to help its members overcome intense public speaking fears. For her, it was successful.

Cain argues that stimulation plays a vital role: A person’s preference for external input is likely the single biggest difference between introverts and extroverts. Psychologist Hans Eysenck developed a theory that says humans will always seek out just the right amount of stimulation. Extroverts will seek out more; introverts, less. He focused his work on the ascending reticular activating system (ARAS).