Listen and driving 'as bad as drink driving'

Listening and driving can be as dangerous as drinking and driving, says a new study.

	Scans of the brain showing the decrease in activation when listening as well

A car radio or a gossipy passenger can impair driving in a similar way to drinking, so that a driver is more likely to weave in and out of the borders of a lane on a motorway, says the professor who led the new research.

Earlier work has shown that the ability of a driver to focus on a task - what scientists refer to as selective attention - depends on the availability of brain resources and much focus has been placed on the safety of mobile phone use in the car, which diverts and taxes these mental resources, so drivers can become distracted, with tragic consequences.

Now, in the journal Brain Research, an American team led by British born Prof Marcel Just, concludes that an even simpler task - listening to someone speak while driving at the same time - "reliably degraded driving performance".

As for how it compares with the effects of alcohol, Prof Just says: "No quantitative comparison has been done determining what blood alcohol level produces similar impairments to listening on a cell phone."

Prof Just, Timothy Kellera and Jacquelyn Cynkara of Carnegie Mellon University, Pittsburgh, hooked 29 participants - 14 women - up to an MRI brain imaging scanner while they were steering a car along a winding virtual road. The participants not only steered, but also listened to general knowledge sentences and verified them as true or false using response buttons in their other hand.

Reaction time and response accuracy were monitored and performance on the simulated driving task was assessed.

The study shows that the addition of a listening task decreased the brain activation associated with performing a driving task by 37 per cent.

Using measures of performance on the simulator, the researchers observed that driving while listening resulted in "much poorer quality of driving". For example, the volunteers made more errors in lane discipline, such as deviating from the middle and hitting a guardrail.

Previous studies had suggested that driving and listening used two different parts of the brain and could work independently of each other, thus allowing the driver to "multi-task" safely.

Driving and listening are two different tasks known to draw on different brain networks - driving is perceptual-motor and listening is cognitive - but the authors cite recent data that indicate one can impact the other. This is backed by the "striking" results of the new study, says Prof Just: it doesn't matter how different the tasks are, the brain can only do so much at one time.

From listening or tuning in to a radio station, to eating or drinking, to monitoring children or pets - all can be distractions and can cause problems for the driver and others on the road. "Drivers need to keep not only their hands on the wheel; they also have to keep their brains on the road," says Prof Just.