For most of us, looking at an image of an attractive man or woman is, to some degree, appealing. Advertisers know this, and so it's not uncommon to see scantily clad people in ads for products besides underwear--say, sports cars or jewelry--that have little or nothing in common with the scantily clad person. Read on.

Psychology suggests the model's sex appeal triggers chemicals in our brains that essentially turn off our moral compass. This is the physiological explanation for our purchases.

Consider this remark from Bram Van den Bergh, a researcher at Katholieke Universiteit Leuven in Belgium, published in Psychology Today. "If your brain's reward regions are activated at the moment of a decision—for example, through exposure to sexual cues—you become more likely to choose impulsively."

One brand that proves the impulsive storm in our brains is Abercrombie & Fitch, though certainly there are more brands whose, ahem, modus adverandi includes scantily clad men, women—and hunky teenage boys. Martin Lindstrom is a branding strategist who says that the secret to A&F's success begins with sex but is taken a step further, into the realm of controversy.

"Sex plus controversy may well equal the world’s most powerful marketing cocktail," writes Lindstrom on Branding Strategy Insider. "The mix guarantees to create a handful of enemies and an army of fans. It’s a dangerous cocktail too. Go too far and your marketing department’s inbox may become jammed with complaints. Then again, if you provoke the right amount of controversy, legal action could put your brand name on everyone’s lips."

But what happens in the brain exactly? If you believe the theory of brainjacking, as described in the Sunday Times, it goes like this: "In a simplistic example, a scientist might show a picture of a scantily-clad woman to a man, and then see the parts of the brain associated with sex and lust lighting up as they consumed more oxygen. Meanwhile, the areas linked to reasoning and morality might go dark as they rapidly shut down. "

So there you have it. Certainly there's more to this notion, but the next time you look at a sexy ad consider the way it makes you feel. Then go out and buy that sports car.