Web sites that automatically customize themselves for each visitor so they come across as more appealing or simply less annoying can boost sales for online businesses by close to 20%, MIT research says.

These sites adapt to display information so everyone who visits sees a version best suited to their preferred style of absorbing information, say the four researchers who write about such sites in "Website Morphing", a paper being published this month in Marketing Science.

So the site might play an audio file and present graphics to one visitor, but present the same information as text to the next depending on each person's cognitive style. Morphing sites deduce that style from the decisions visitors make as they click through pages on the site.

"You need five to 10 clicks before you can really get a pretty good idea of who they are," says John Hauser, the lead author of the paper and a professor at MIT's Sloan School of Management. He says over the past decade statistics have evolved to allow broader conclusions from less data.

"You can infer a lot more from a lot less data by borrowing data from other respondents," he says. "When I first heard it I thought this couldn't possibly work."

But it does. By using a sample set of users navigating a test Web site, individual businesses can set the baseline for what click choices on that site mean about the visitor. Over time with real potential customers visiting a live site, the morphing engine fine tunes itself to draw better conclusions about visitors' preferences and to serve up what pages most likely lead to a sale, Hauser says.

The software is open source and available at MIT's Web site, but so far no one has created a commercial business to apply it to individual customers, he says.

Such auto-customizing Web sites are less intrusive than the alternative - sites that visitors can manually customize, a time-consuming process that many visitors won't bother with, the researchers say. And they create the right Web site for maximum sales much quicker, Hauser says.

They tested out their theory on 835 current U.K. broadband users or those interested in broadband who were paid to fill out questionnaires and navigate a sample BT Web site for broadband services.

They concluded that if the site had perfect information about each person's cognitive style, it could boost sales 21%. Even with partially known cognitive styles, the site could boost sales nearly 20%, they say.