All sorts of behaviors can prove addictive—eating, shopping, sex, video gaming, gambling, even Twitter! How else to explain these Canadian coeds tweeting all bundled up when they could be defrosting on the beach in the Florida sun? More on the limbic system and addiction in Section 6-3; motivation and emotion, Sections 12-3 and 12-4; memory, Section 14-3; and brain disorders, Focus 16-1 and Section 16-4.

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