You can’t say no to Citi’s robo-clickbait by Robert Hackett @FortuneMagazine February 19, 2015, 7:43 PM EDT E-mail Tweet Facebook Linkedin Share icons In the annals of marketing, no anti-littering slogan has ever held more swagger or sway than “Don’t mess with Texas.” Appealing to an audience’s emotions works: In the decade or so after that campaign appeared, stray trash plummeted statewide. Now imagine if salesmen had that power of persuasion—or better yet, robot salesmen. That’s the kind of manipulative mastery Citibank is employing in its marketing departments in an attempt to boost the success of its promotional emails. Citi’s marketing missives use natural-language processing—a blend of artificial intelligence and linguistics—to generate sentences and phrases that customers can’t help clicking. The idea is to trigger an emotional response (and index-finger twitch) that might translate into sales. “It eliminates the guesswork of copywriting,” says Alex Vratskides, CEO of Persado, the startup behind the tech. Three-year-old Persado says it has distilled the spectrum of human emotion into 19 categories—such as gratitude, fear, and love—all for the purpose of calling customers to action. The company says it has tens of millions of ways of phrasing email subject lines and has identified, for instance, 250 different ways to say “Call now.” By generating all possible word combinations in a given semantic space and testing a subset, it’s able to deploy the one that best rouses a response. The dispatches, though coolly calculated, tug consumers at their core. “It’s like generating the most beautiful woman from the best possible genes,” says Vratskides, grinning. “Think of these as genetically engineered marketing messages.” Citi, for one, has lots of reasons for employing machine-learning technology in its communications: to sell credit cards, to persuade customers to upgrade or open new checking accounts, to coax people into spending rewards points. If it’s going to contact customers anyway, why not tailor the messages to be as engaging as possible? Persado says Citi has seen a 70% increase in the “open rate” of its emails and a 114% increase for the “click-through rate” within them. (Though Citi acknowledged that it uses the technology, it declined further comment.) The bank seems to have had such success with the software that Citi Ventures, its investment arm, participated in Persado’s second round of funding along with American Express Ventures and Bain Capital Ventures. It totaled $21 million. And what would robo-marketers make of “Don’t mess with Texas”? David Atlas, a Persado marketer, can’t resist a rhyme: “We call this persuasion automation.” This story is from the March 1, 2015 issue of Fortune.