The younger volunteers also didn't seem to be affected when the scientists sped up the time at which the cars approached the intersection by shortening the bumper-to-bumper distance between cars.

Just ask Toyota, a firm that once had a peerless reputation for reliability but spent much of last year battling allegations that its cars had defective accelerators.

The Californian company's small plug-in sports car can accelerate from zero to 96kph in 3.7 seconds.