Texting at the wheel is one of the most dangerous activities motorists can undertake, causing a key safety function in the brain to stop working, the results of a study suggest.
Sending texts at the same time as driving prevents the brain's "autopilot" function from functioning efficiently, according to the research.
Scientists asked 59 volunteers to drive along a simulated road while being put off by a series of distraction.
Participants were asked mentally challenging questions, emotionally charged questions and presented with what researchers called "texting trivialities".
All three led to "jittery" steering, but only the last caused significant lane deviation and unsafe driving.
Texting caused a breakdown in the brain's 'error-correction system', which intervened in other situations to get the participants out of trouble.
Lead researcher Dr Ioannis Pavlidis, from the University of Houston, US, 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.
Copyright Press Association 2016. Motoring News articles do not reflect the RAC's views unless clearly stated.