That blurry, numb sensation you feel just behind your eyes? Yeah, you've been staring at a computer screen for far too long. According to a recent study, Americans spend an average of 8 hours a day staring at screens--TVs, PCs, cell phones, and so on. About 61 minutes of that time is spent taking in TV ads.

The dominant form of media delivery in most Americans' lives remains the TV, according to the $3.5 million study conducted by Nielsen. The PC has edged into second place, though, beating out the radio, with the struggling world of print in fourth place.

The study also found that most age groups spend about the same amount of time sitting in front of screens. 45-to 54-year-olds actually rack up the highest daily rate, with an hour more than other groups.