doctor william hori as a researcher at liberty mutual, and took 17-year-old samantha garcia, of north hampton, for a spin on a test track to show her how distracting it can be. the most common apps used by teens are music and navigation. our cameras clearly show how the navigation app repeatedly pulls her eyes away from the road. >> even a short glance away from the road can have a profound impact on your ability >> i felt like i should not be doing it, it is definitely my eyes off the road. >>reporter: a psychiatrist, at mass general, says this study is different, because they used a series of visual tests to measure the teen's, and not just what they say. >> you ask kids if they want to use their apps, and they will say that's too dangerous. but then in the moment, something happens. >> i feel like i wasn't really looking at the roads. >> doctor hori took me out on the test track and observed as i was programming a navigation app. >> it is inconsistent. you don't look up for long enough to really get an idea what you are doing. >>reporter:the city's authors suggest keeping the phone