English: Darwin XI's environment and experimental protocol. (A) Darwin XI at the choice point of its plus-maze environment. Darwin XI began a trial alternately at the east or west start arm and used its artificial whiskers to follow the maze arm until it reached the choice point. As it followed the maze wall, its whiskers sensed patterns of pegs, its camera sensed color cue cards on the perimeter, its compass provided heading, and its laser provided range information. (B) In the beginning of training, Darwin XI was given a rewarding stimulus when it chose the south goal arm (B1). After it successfully learned that task, the rewarding stimulus was switched to the north goal arm (B2).