When it comes to getting things done, multitasking is a bane not a blessing, according to Stanford University researchers.
While web users may be simultaneously listening to iPods, watching online video, instant messaging, checking email and firing off Facebook updates, they likely aren't doing any of it well.
"They're suckers for irrelevancy," said Stanford communication professor Clifford Nass, whose research team released its findings this week.
"Everything distracts them."
Stanford researchers concluded that people prone to juggling streams of input such as emails, web searches, text chats and video perform worse than those who prefer to handle one task at a time.
"We kept looking for what (multitaskers) are better at, and we didn't find it," said Eyal Ophir, the study's lead author and a researcher in Stanford's Communication Between Humans and Interactive Media Lab.
Social science has long held that people can't process more than one string of information at a time, according to the researchers, who wanted to figure out how multitaskers evaded that rule.
They aren't exempt from that rule, according to tests conducted with 100 students divided into heavy multitaskers and one-task-at-a-time types.
"(Multitaskers) couldn't help thinking about the task they weren't doing," Mr Ophir said.
"They can't keep things separate in their minds."
Testing also showed that multitaskers weren't superior when it came to remembering or organising information in their minds.
Researchers showed students letters and asked them to remember repeated appearances.
"The low multitaskers did great," Mr Ophir said.
"The high multitaskers were doing worse and worse the further they went along because they kept seeing more letters and had difficulty keeping them sorted in their brains."
The researchers are trying to figure out whether chronic multitasking is ruining people's ability to concentrate or whether people born that way are drawn to multitasking.
"When they're in situations where there are multiple sources of information coming from the external world or emerging out of memory, they're not able to filter out what's not relevant to their current goal," said researcher Anthony Wagner, an associate professor of psychology.
"That failure to filter means they're slowed down by that irrelevant information."