The use of visual information for planning accurate steps in a cluttered environment.

When an observer walks across irregular terrain, he uses vision to plan his steps. How far in advance of each step does he acquire the critical information? We trained cats to walk accurately down a cluttered alley, and then turned out the light in mid-trial. Cats usually continued to walk without error for one to four steps, indicating that they had acquired the information to guide each step well before foot contact.