Science has already proven that multitasking doesn't make you more productive (in fact it makes you dumber--there's even a test you can take to prove this to yourself if you'd like). But new research goes even further. Not only is multitasking not helping you get more done, the study out of the University of Sussex in the UK indicates, it might actually be physically harming your brain.

The research looked into the incredibly common practice of "second screening," i.e. keeping your laptop open or sending texts while you watch TV, for example. Seventy five British adults were given a questionnaire about their multitasking habits and then given an MRI by the team. The results showed a significant difference between the brains of heavy multitaskers and others: those addicted to using multiple devices simultaneously has lower gray matter density in a brain area called the anterior cingulate cortex (ACC), which is linked to emotional control and plays a role in decision-making, empathy and how we respond to rewards.

Earlier research has shown a link between heavy multitasking and emotional issues such as poor attention span and anxiety, but this "study was the first to reveal links between media multitasking and brain structure," neuroscientist and study co-author Kep Kee Loh commented.

While the results can't conclusively prove that all those second screens are causing the changes to the brain (differences in brain structure could also lead people to be more likely to multitask), the researchers suggest that the results should nonetheless serve as a red flag for fans of multiple devices while further studies are carried out to test causality.

"Media multitasking is becoming more prevalent in our lives today and there is increasing concern about its impacts on our cognition and social-emotional well-being," Kee Loh said. "I feel that it is important to create an awareness that the way we are interacting with the devices might be changing the way we think and these changes might be occurring at the level of brain structure."

So keep that in mind the next time you're tempted to carry on an IM exchange while watching your favorite show or squeeze in a few emails at the same time you check out that training video.