"I use voice, so I'm not looking"

The newer version of the belief has moved from the hands to the eyes. You don't hold the phone and you don't look at it. You say the message and it types it, you ask for the song and it plays, you tell it to ring someone and it rings. Eyes ahead the whole time. Surely that's solved.

Strayer, Joel Cooper and colleagues took two hundred and fifty-seven people and had each of them use the voice system in one of ten new cars, then gave them the car for five days to practise, then measured again. They rated the mental workload of using the systems as moderate to high, on average 3.34 out of 5, and it varied with how well designed the system was and how long the task took. Practice didn't fix it. Tasks that were hard on day one were still hard after a week. And the cost didn't stop when the task did. There were residual effects after the interaction had ended, meaning the driver's attention took time to come back even once they'd stopped talking to the car.

They ran a similar study on suburban roads with the voice assistants on three phones, placing calls, choosing music and sending texts by voice. Workload was significantly higher than driving alone. While drivers were talking to the phone their measured workload was no different from doing a demanding memory test, and again there was a residual cost that took a while to fade. I'm not printing the brand names, because the systems have changed since and the point isn't which was worst. The point is that none of them was free.

A voice message is a conversation with a machine that doesn't know you're driving, plus the composing of the message, plus the checking that it heard you. It's a tap you've left running in another room, one sentence, and that's the only analogy in this chapter. Eyes on the road, and some part of you listening for the overflow.

I'm not saying never use voice. If you must take a call, a voice command to answer it beats a hand on the phone, and the law agrees. I'm saying the belief that voice makes the phone cost nothing is the newest of the beliefs and the one with the freshest evidence against it.