i click when a green light flashes, simulating something on the road that needs my attention. i drive listening to the radio. ♪ another trip with speech to text, hearing and answering an e-mail. >> i haven't heard from you in a while. >> reply. >> what would you like to say? >> reporter: i will talk to you soon. send. i click the button. but -- how did i do, joel? >> your response times were a bit delayed when you were engaged in the speech to text task. >> reporter: here's what real estate . >> reporter: here's what researchers from aaa found. the least amount of distraction was the radio. going up the scale. talking on hands-free phone. talking to a passenger. hand-held phone was next. the speech to text programs causing the most distraction. a fraction of a second which can be dangerous. they call it inattention blindness. >> even if your hands are on the wheel and your eyes are on the road, you may not be safe. >> reporter: automakers say the study sends a misleading message suggesting hands-free and hand-held devices are equally risky. the risk, says aaa, is that