Need a hand at the soup kitchen this weekend? Better ask someone less talkative. A new study suggests cell phone use encourages selfish behavior.

The study (detailed in the working paper, “The Effect of Mobile Phone Use on Prosocial Behavior”), looks at the behavior of male and female college students, mostly in in their early 20s. They participated in a series of experiments that tested the way mobile phone use shapes prosocial behavior, which the study defined as action that helps another person or society in general. (Nope, encouraging people to sign up for Twitter to raise your Klout score doesn’t count.)

Turns out cell phones can cause some serious selfishness. People were less likely to volunteer for charity when they used a mobile phone for three minutes than those in a control group. In fact, they were even more selfish thanpeople who spent the same amount of time browsing Facebook. Researchers also compared the effects of drawing and thinking about cell phones to sketching and thinking about television, and the cell phone sketchers also failed selflessness tests— they were much less likely to find words related to others in a word search puzzle.

The study authors say using a cell phone satisfies the need to connect with others. So a few minutes of LMAO-ing temporarily might decrease our interest in the people around us. And, according to the study authors, these same findings could apply to people in general— not just text-obsessed twenty-somethings.

Other research has yielded similar findings—one study found people using cell phones in public places are less friendly to strangers than people who aren’t blabbing into the receiver. (Plus they can be seriously annoying— who really wants to hear about someone else’s relationship drama?) And be suspicious the next time a date says he’s just got to take this phone call— some Americans pretend they’re on a cell phone conversation to avoid talking to people around them. But don’t advocate banning the Blackberry just yet. Other research suggests high school students are less lonely when they maintain an active social network through cell phone useMobile-phone e-mail use, social networks, and loneliness among Japanese high school students. Ogata, Y., Izumi, Y., Kitaike, T. Department of Community Health Nursing, School of Nursing, Chiba University. Japanese Journal of Public Health 2006;53(7):480-92..

There’s no need to resort to carrier pigeon to communicate with pals. “It’s more about being aware of this possible influence on behavior,” says study co-author Dr. Rosellina Ferraro. And of course keep in mind all the other risks associated with digital technology— a face full of bacteria might be worse than some selfishness.