A device that warns motorists when they are too upset to drive safely or picks up when they are texting is being developed by engineers in the US.The ''stressalyser'' picks up jittery movements on the steering wheel, which occur when a driver makes micro-adjustments to correct errors caused by loss of concentration.Developers at the University of Houston want to build the sensor into steering wheels to alert the driver that they need to stop the car. It could even slow the vehicle.Research has shown that feeling sad, angry or agitated behind the wheel raises the risk of an accident by nearly 10 times."This system may serve not only as a black box in car accidents, but also as a driver alert and prevention mechanism, since it will continuously sense a driver drifting to distracted mode," said Ioannis Pavlidis of the University of Houston.In an experiment, 59 drivers were asked to drive in a simulator. Once they were fully focused they were distracted by emotionally charged questions.The researchers found that the drivers' handling of the wheel became jittery ."A likely explanation for this is the function performed by a part of the brain called the anterior cingulate cortex, or ACC," said Pavlidis."ACC is known to automatically intervene as an error corrector when there is psychological conflict."In this case, the conflict comes from the cognitive, emotional and sensory motor stressors."This raises the levels of physiological stress, funnelling energy to the driver's arms, resulting in jittery handling of the steering wheel." - ..