If you really want to know something, don't email your question to hordes of people. Researchers have found that the more people you email, the more likely each recipient is to ignore it.

Greg Barron and Eldad Yechiam emailed 240 colleages at Technion Israel Technology Institute -- individually or in a group -- to find out response rates. Posing as a female student, they asked people if the institute had a biology faculty.

Replies ranged from "very helpful" (with extra information) to plain brusque "Look on the web page!". Others simply tried to chat "her" up.

Only half of group recipents responded, compared with 64 percent of those with just their own name in the "To" box. Single recipients were also twice as likely to be "very helpful".

"Like bystanders at a crime scene, people assume that someone else will help," says Barron. "So if you want a volunteer to bring a cake to Monday's meeting, sending an email to lots of people might not be the way to go."