Do you or someone you know (like your teenager): Send instant messages while surfing favorite websites; watch TV while texting; or maybe try to do all of these in rapid succession, with some tunes on the background, of course.

A recent Stanford University study says that this multitasking lifestyle may be messing with your mind.

In tests that measured attention, memory and the ability to switch tasks, heavy media multitaskers came out second best to those who prefer tackling one task at a time.

The heavy multitaskers couldn't help thinking about the task they weren't supposed to be doing and didn't focus well on the one they were supposed to be doing.

Researchers split around one hundred students into two groups; those who regularly engage in media multitasking and those who don't. Then the competition began.

The first test measured the ability to pay attention and filter out irrelevant information. Subjects were shown two different screens of images. The first showed two red rectangles. The second showed two red rectangles surrounded by two, four or six blue rectangles. The subjects had been instructed to pay attention to the red rectangles and ignore the blue ones. The task was to determine if the red rectangles were in the same position or had moved in the second screen. Each screen was flashed twice.

The heavy multitaskers were distracted by the blue rectangles and performed horribly on this test. Strike one.

The second test was on memory. The subjects were shown screens containing sequences of letters. At some point subjects started being asked if a particular letter was making a repeat appearance or not. The low multitaskers scored well at this. The high multitaskers scored poorly. And their performance got worse and worse as more screens of letters were flashed. Apparently, they had difficulty keeping the letters sorted in their memory. Strike two.

The third test measured the ability to efficiently switch from one task to another. The subjects were shown screens containing both letters and numbers, and told which to focus on. At times they were told to pay attention to the numbers and tell whether they were odd or even. At other times, this switched to determining whether the letters were consonants or vowels. Once again, the light multitaskers outperformed the heavy ones. The heavy multitaskers couldn't help thinking about the task they weren't supposed to be doing and didn't focus well on the one they were supposed to be doing.

And that's strike three.

Social scientists have long assumed that it's impossible to process more than one string of information at a time. But many researchers have suspected that people who seem to be multitasking must have some type of mental edge. The Stanford researchers had set out to try to find what multitaskers are better at. But in these three tests, nothing showed up.

Communications professor Clifford Nass, one of the study authors, explained the multitaskers' poor performance, perhaps uncharitably: "They're suckers for irrelevancy. Everything distracts them."

This study can't tell if multitasking is worsening people's mental abilities or if people who aren't good at these abilities in the first place are the ones most attracted to multitasking. But the researchers are convinced that the minds of media multitaskers are not working as well as they should be.

The results of the study were published in the August 24, 2009 edition of the Proceedings of the National Academy of Sciences.