ABSTRACT
The foundation of vision for all seeing animals is the optic flow field, the changing pattern of light reflected from the environment to a moving eye. Controlling velocity of approach using tau-dot is fundamental in movement control and has been shown to be involved in many different contexts — for example, in humans reaching, braking, catching, hitting, and landing from a somersault, as well as in hummingbirds docking on a flower, and in pigeons and bats landing. The chapter analyses whether velocity of approach in slalom skiing was controlled using tau-dot. Negotiating slalom flags in skiing requires controlling the velocity of approach of the skis accurately around the flags in order to save valuable seconds. The chapter also analyses whether negotiating slalom flags as fast as possible was achieved by perceptually regulating the force applied to the snow so as to keep the ratio impulse/force proportional to the time-to-contact with the slalom flag.
