The design of robotic controllers through evolutionary methods requires making a large number of choices about the experimental setup, which are often left to the expertise or naivete of the experimenter. Although much attention is normally given to the fitness function or the genotype-to-phenotype mapping determining the robot controller, the robot configuration is often selected with little care. Yet, an ill-defined configuration-in terms of the selected subset of the sensory-motor system, or in the pre-processing of the raw sensor data-may be decisive in determining the outcome of the evolutionary process. In this paper, we study the effect of different robot configurations on the ability to evolve efficient behaviors for a swarm robotics system. In this domain, the choice of a good configuration is fundamental as even small details can lead to large differences in the group behavior. To demonstrate the importance of the robot configuration, we test different alternatives and measure the group performance on a bi-objective scale. We find that different configurations not only have a strong effect on performance, but they also correspond to behaviors with radically different features concerning the organization of the group.
