Eye movements coordinated with steering benefit performance even when vision is denied.

When driving along a winding road, eye movements and steering are tightly linked. When approaching a bend, the driver looks across to the inside kerb (the tangent point) some time before turning the steering wheel. All drivers we have tested show this optimal coordination, without which driving is impaired. An intriguing question is how much of the benefit for steering arises just from moving the eyes in this coordinated way (ahead of steering and in the same direction), and how much from the visual information that the eyes move to acquire, in this instance the foveated tangent point. This can be answered by dissociating the two, by reducing visibility of the road ahead (and crucially of the tangent point) to a level at which drivers might or might not choose to move their eyes but, if they do, will not gain the information they seek. Twenty subjects repeatedly drove a simulated stage of the World Rally Championship. With full visibility, they exhibited the usual coordination of eye movements and steering. Subsequently, visibility was reduced on the left hand side. Drivers who persisted in making eye movements coordinated with steering to the left, despite the fact that they could no longer see the tangent point on that side, performed better than drivers who under the identical conditions did not look to the left. This confirms that the making of coordinated eye movements itself benefits steering, even when the eye movements do not yield the visual information sought.