Multitasking with iPad or cellphone in hand can be potentially dangerous—think texting while driving. Other times, multitasking might just be dangerous to grade point averages, such as, say, looking at LOLCats pictures during a college lecture. Some hardcore digital natives insist, however, that they—and their brains—can effectively handle two or more things at once.

Professor Steven Yantis’ brain imaging studies suggest otherwise.

“People’s assumptions that they can really work on multiple tasks at the same time is likely not to be correct,” says Yantis, a professor in the Department of Psychological and Brain Sciences, who has used functional magnetic resonance imaging to examine how the brain handles more than one source of stimuli.

“If they are listening to a lecture and also checking their cellphones they are, in fact, switching between tasks, and as they direct attention to one of those two tasks, they lose track of the other task—and maybe without even being explicitly aware of it. Depending on the content of these two sources of information, you are going to lose some of your ability to encode and remember what is coming from one or the other.”

And sometimes what our brain chooses to focus on happens beyond our conscious control. One of the lab’s more recent studies found that when certain visual stimuli become identified with receiving a reward, our brain gives them more attention—even long after the stimuli cease to provide the reward.

In this test, subjects searched for objects on a computer screen, and when they found, for example, the red ones, they were given a reward (money in this case, but other studies have looked at rewards such as food or something else pleasurable). Later he had the subjects do a completely different type of search where object shape was important and color was irrelevant (and offered no rewards). Imaging showed that the brain continued to respond differently to the previously rewarded red stimuli, though the subjects themselves denied they gave it any special attention. And this was true even if the second test was conducted [as much as] six months later.

“How attention works has been a key part of my research for the past 25 years,” Yantis says. “Changes in technology, to some degree, are driving some of these differences in how people manage multiple sources of information.”

Might our brains physically evolve to keep up with our gadgets? “I don’t think we know that, to be honest with you,” Yantis says. “This transition to multiple sources is happening now.”