An “autopilot” in the brain that prevents distracted drivers steering into danger breaks down when texting at the wheel, research has shown.
The findings suggest reading or sending text messages is an especially hazardous activity for motorists.
In tests, 59 volunteers were asked to “drive” along a simulated road while scientists did their best to put them off.
Three types of driver distraction were studied – mentally-challenging questions, emotionally-charged questions and “texting trivialities”.
Each of them caused steering wheel handling to become “jittery” – but only texting distractions resulted in significant lane deviation and unsafe driving.
When dealing with distracting texts, the drivers received no help from an unconscious “error correction” system in the brain that in other situations intervened to get them out of trouble.
Lead researcher Dr Ioannis Pavlidis, from the University of Houston in Texas, said: “The driver’s mind can wander, and his or her feelings may boil, but a sixth sense keeps a person safe at least in terms of veering off course.
“What makes texting so dangerous is that it wreaks havoc into this sixth sense. Self-driving cars may bypass this and other problems, but the moral of the story is that humans have their own auto-systems that work wonders, until they break.”
The “autopilot” is situated in the anterior cingulate cortex (ACC) region of the brain, said the scientists.
Stress from external distractions fed “fight or flight” energy into the drivers’ arms, resulting in the jittery wheel handling.
But then the ACC stepped in, counterbalancing any strong jitter to the left with an instant matching jitter to the right, and vice-versa. The net effect was that any veering to the left or right was avoided, and the vehicle remained accurately on course.
Texting disrupted this system, allowing jittery handling of the steering wheel to go unchecked.
Dr Pavlidis added: “Following up on the results of our science study, we are currently looking into the development of a car system to monitor outward driving behaviours, such as steering jitter or lane deviation, as well as the internal state of the driver that causes them.”
The research is described in the journal Scientific Reports.
Steve Gooding, director of the RAC Foundation, said: “This work echoes previous research by the Transport Research Laboratory for the RAC Foundation.
“It found that texting at the wheel impairs drivers’ reaction times by over a third, more than being at the legal drink-drive limit or under the influence of cannabis.
“In 2014, 24 people were killed on Britain’s roads in accidents where the driver being distracted by the use of a mobile phone was a contributory factor.”