Today we know that the reality is far more complex. For one thing, the ARAS doesn’t turn stimulation on and off like a fire truck’s hose, flooding th… - Susan Cain

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Today we know that the reality is far more complex. For one thing, the ARAS doesn’t turn stimulation on and off like a fire truck’s hose, flooding the entire brain at once; different parts of the brain are aroused more than others at different times. Also, high arousal levels in the brain don’t always correlate with how aroused we feel. And there are many different kinds of arousal: arousal by loud music is not the same as arousal by mortar fire, which is not the same as arousal by presiding at a meeting; you might be more sensitive to one form of stimulation than to another. It’s also too simple to say that we always seek moderate levels of arousal: excited fans at a soccer game crave hyperstimulation, while people who visit spas for relaxation treatments seek low levels.*