Marketers understand that humans, like other animals, have evolved finely tuned mechanisms for competing for status—and that our choice of a consumer brand is less about the material item itself and more about advertising our wealth, beauty and power to (hopefully jealous) onlookers. But in his new book, Spent, evolutionary psychologist Geoffrey Miller argues that our species is also driven to show off such characteristics as agreeableness (see Whole Foods and Fair Trade coffee) and conscientiousness (see a well-maintained lawn). While Miller thinks it's improbable that humans will ever give up "their runaway quest for self-display," he notes that our instincts to show off, say, kindness and intelligence can privilege different forms of consumption. For example, we're already seeing a shift away from items that scream "I can afford to waste outlandish amounts of resources!" (big yachts, caviar-and-champagne blowouts) to items that trumpet "I'm ecoconscious!" (electric cars, organic eggs). Guess the phrase "green with envy" is about to take on a whole new meaning.