When you need a favor, there's nothing more convenient than shooting off an e-mail or two. It also saves you the awkwardness of in-person pleading. Just don't expect the same results.

Two new studies show that people nonetheless believe e-mail requests are just as effective as asking face-to-face. In the first study, published in the March issue of the Journal of Experimental Social Psychology, 45 participants were told they would have to ask 10 strangers, either in person or via e-mail, to complete a survey for no pay. People in both groups said they expected one in two strangers to agree, and both were wildly wrong. More than 70 percent of people approached in person complied; among those who received e-mails, the response rate was just 2 percent.

In a second study, people were recruited to complete a paid survey via e-mail or in person. Before they began the paid survey, they were offered the chance to complete a second, unpaid one. Again, canvassers underestimated in-person compliance and overestimated e-mail responses to the unpaid task. The e-mailers had an inflated idea of how much people trusted them and how much empathy they garnered. “If people want to have more effective e-mail messages, they have to include more personal information to facilitate building initial trust,” says Mahdi Roghanizad, a business professor at Western University in Ontario, Canada, who co-wrote the paper.

What about soliciting a friend or colleague? Face-to-face is still best, preliminary data suggest. “When a friend comes to you and asks in person,” Roghanizad says, “it means they are in serious need or respect you enough to pay a visit.”