During a recent panel on advertising held by The Wharton School, a marketing and advertising strategist said the key to strong sales is inducing emotion. 

"Whether it is pensions or pet food, decisions are made emotionally," said Orlando Wood, managing director of Brain Juicer Labs. "If you can give people reasons afterward [for why] they made the right decision, so much the better. If you can give them post-rationalization, then you may have won them for good."

Daniel McDuff, a PhD. candidate at the Massachusetts Institute of Technology who studied the effectiveness of advertisements while recording people's facial expressions and reactions to campaigns, agreed. The advertisements that generated the most sales, he said, made people smile. "[The ad] has got to make you feel something for the brand."

Good advertisers harness something Anne Rivers of BrandAsset Consulting and Baylor University professor Kirk Wakefield call "brand love." It's what Citigroup did when it purchased the naming rights to the new Mets stadium and named it Citi Field. By associating their brand with America's favorite pastime as well as the New York baseball team, consumers found themselves viewing the financial services firm in whole new light. Under Armour, the clothing and sporting goods company, found success once it began working with little league teams. 

The bottom line: "Fame and emotional advertising is the best predictor of effective marketing and sales just about every time," said Wood.

So the next time you work an ad campaign, make sure it makes you smile.