"Why is it impossible to stop thinking, to render the mind a complete blank?" a Scientific American reader wonders.
The answer comes from Barry Gordon, professor of neurology and cognitive science at the Johns Hopkins University School of Medicine.
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Constant thinking is what propelled us from being a favorite food on the savanna—and a species that nearly went extinct—to becoming the most accomplished life-form on this planet. Even in the modern world, our mind always churns to find hazards and opportunities in the data we derive from our surroundings, somewhat like a search engine server. Our brain goes one step further, however, by also thinking proactively, a task that takes even more mental processing.