Should we multtask just because we can?

It's the era of the split attention span, for better or worse. The people who text and drive. The colleagues who sit through meetings while trolling their iPhones. The teens who study and watch TV, listen to music and monitor texts all at once.

Researchers have been gathering new evidence about how and why we multitask, and learning that juggling things is neither a guarantee of success nor always doomed to fail.

One recent study led by Ohio State University communications professor Zheng Wang found that college students who watched TV while reading or studying didn't do as well at their main task, but felt better about it than those who turned the TV off, because they felt more entertained and relaxed.

The findings were based on activity logs - electronic, of course - maintained by 32 students over a four-week period.

While some people may think such multitasking makes them more productive, the study showed "they are not being more productive, they just feel more emotionally satisfied from their work," Wang said.

However, other studies seem to show that some people are better at multitasking than others - particularly when drawing information from different senses.

Last month, Kelvin Lui and Alan Wong at the Chinese University of Hong Kong reported that people ages 19 to 28 who frequently use different types of media at the same time seem to be better at integrating information from multiple senses when asked to perform a specific task. "Media multitasking may not always be a bad thing," the authors concluded in a report published online by Psychonomic Bulletin and Review.

Compared to so-called "light multitaskers" (based on questionnaires about media usage), those who media multitasked the most were better able to pick up information from seemingly irrelevant sources. A total of 63 people were tested.

The task was to search for a visual target on a screen, which changed color from time to time. During half the experiments, an audible tone sounded just as the image changed colors. The light multitaskers were much better at running down the target when there was no sound cue, but with the sound added, the frequent multitaskers were much better at finding the image.

Of course, there may be times where multitasking has to happen. Ask any air traffic controller, combat soldier or parent.

Still another study carried out last year by communications researchers at the University of Texas at Austin found that 20- to 24-year olds have conflicted views on multi-tasking, at least in the workplace.

Multitasking voluntarily is one thing, but being expected to handle several things at once by a boss was not always viewed positively by many of the "millennial" respondents the UT researchers interviewed in two focus groups (63 students) six months apart.

Keri Stephens, an assistant professor and lead author of the study in published in the January issue of Human Communications Research, said many students have confessed they don't consider themselves well-suited to juggle several tasks a once. The responses in the study focus groups revealed that many see "simultaneous multitasking" in a job description as meaning they'll be expected to work or be available outside normal hours.

Finally, an experiment described by University of California at Irvine researchers during a computing conference in Austin in early May gives some hint about the health impacts of multi-tasking.

Volunteers who regularly worked on computers at an Army support center outside Boston were studied using heart monitors and software sensors. Half had their email turned off during the workday.

Over a five-day period, those cut off from email reported feeling better able to do their jobs and stay on task, with less stress and fewer time-wasting interruptions. Those with email changed reading panes on their screens an average of 37 times an hour; those without, about 18 times an hour. And the hearts of the email users were in a steady "high alert" state with more constant rates; while those who were cut off experienced more natural, variable heart rates across the workday.