"Don't work too hard," wrote a colleague in an e-mail today. Was she sincere or sarcastic? I think I know (sarcastic), but I'm probably wrong.

According to recent research published in the Journal of Personality and Social Psychology, I've only a 50-50 chance of ascertaining the tone of any e-mail message. The study also shows that people think they've correctly interpreted the tone of e-mails they receive 90 percent of the time.

"That's how flame wars get started," says psychologist Nicholas Epley of the University of Chicago, who conducted the research with Justin Kruger of New York University. "People in our study were convinced they've accurately understood the tone of an e-mail message when in fact their odds are no better than chance," says Epley.

The researchers took 30 pairs of undergraduate students and gave each one a list of 20 statements about topics like campus food or the weather. Assuming either a serious or sarcastic tone, one member of each pair e-mailed the statements to his or her partner. The partners then guessed the intended tone and indicated how confident they were in their answers.

Those who sent the messages predicted that nearly 80 percent of the time their partners would correctly interpret the tone. In fact the recipients got it right just over 50 percent of the time.

"People often think the tone or emotion in their messages is obvious because they 'hear' the tone they intend in their head as they write," Epley explains.

At the same time, those reading messages unconsciously interpret them based on their current mood, stereotypes and expectations. Despite this, the research subjects thought they accurately interpreted the messages nine out of 10 times.

The reason for this is egocentrism, or the difficulty some people have detaching themselves from their own perspective, says Epley. In other words, people aren't that good at imagining how a message might be understood from another person's perspective.

"E-mail is very easy to misinterpret, which not only triggers flame wars but lots of litigation," says Nancy Flynn, executive director of the e-Policy Institute and author of guidebooks E-Mail Rules and Instant Messaging Rules. Many companies battle workplace lawsuits triggered by employee e-mail, according to Flynn.

People write absolutely, incredibly stupid things in company e-mails," said Flynn.