– "Think before you jerk.” “Jerking isn’t a joke." Such slogans, as reported in the Washington Post and elsewhere, garnered national attention when used to remind drivers in South Dakota not to over-correct their steering on slick roads. Indeed, the standard theory behind the way we steer our cars dates back to the 1940s but has left us with a longstanding mystery: data shows that we have a habit of jerking the wheel from time to time, puzzling researchers. Now, experts in Sweden are explaining the phenomenon, and their findings could lead to better safety systems in cars, according to a release at Eureka Alert. The jerkiness is tied to the way humans reach for things: When something is close by, we move our arms more slowly to grab it than we do when it's further away. The result is that both movements take the same amount of time. "We immediately recognized this pattern" as similar to steering behaviors, a researcher says. "It was a bit of a eureka moment. Was it possible that this basic human behavior also controlled how we steer a car?" A study of more than 1,000 hours of drivers' movements suggests that it certainly was. The team developed a mathematical model addressing the behavior; now, "it is possible to predict how far the driver is going to turn the wheel, right when the person starts a wheel-turning movement. It's like looking into the future," the researcher says. That could improve safety: For instance, if a sleepy driver is edging off the road, his car's support system could predict how much he's going to jerk the wheel to try to correct things, often disastrously, and intervene to prevent it. (South Dakota eventually decided to drop the "don't jerk and drive" campaign.)