Fig. 1.

Experimental setup. (A) A food and poison source, both emitting red light, are placed 1 m from one of two opposite corners of the square (3- × 3-m) arena. Robots (small circles) can distinguish the two by sensing the color of the circles of paper placed under each source by using their floor sensors when driving over the paper. (B) The robot used for the experiments is equipped with two tracks to drive, an omnidirectional (360°) vision camera, a ring of lights used to emit blue light, and floor sensors to distinguish food and poison sources (see ref. 14 for details).