## 1 Introduction
In this paper we explore the use of Separable Natural Evolution Strategies (SNES, see [18]), in order to evolve CTRNN neural controllers for different tasks. Another critical design step in swarm robotics is the communication mechanics of the group. Communication within the swarm refers to any kind of interaction among robots in which information about states, actions or intentions of agents is shared across the swarm. According to [19], inter-agent communication in swarm robotics can be split into: Stigmergy, Interaction via state and Direct communication. Additionally, a different division can be provided if the communication technology is considered. Although not very common, long range communications, based on RF systems, have been used in swarm robotics when direction awareness is not an issue and long range global communication is required (see [20; 21; 22]). Middle range communication has also been addressed by means of sound (e.g., [23]) using speakers and microphones to produce and capture sound beeps. In both options, several of the exposed studies break the principle of locality presented at the beginning of the section. Therefore, minimal and short range communications are typically desirable in swarm robotics. For this type of communications, infrared (IR) technology is commonly employed (see [24]). IR sensors and emitters can be used for both distance estimation to solid objects [10; 13; 25; 26], direct communication [27] or both [9]. Apart from its short coverage, IR technology presents several issues such as interferences, ambient light distortion, communication death zones, impossibility to send and receive at the same time or low data rates (see [25; 28] for further details). However, it equally provides numerous advantages that make IR technology highly suitable for local communication in swarms of robots. Firstly, it is highly inexpensive and extremely low consuming, which, provided that swarm sizes can be arbitrarily large and individual robots are notably simple, are utterly desirable features in swarm robotics. Moreover, it allows a directionality awareness in the communication, as in-board IR communication in mobile robots is equipped with a set of receiver and emitters surrounding the robot perimeter. The knowledge of the direction from where neighboring robots are interacting with the agent is highly desirable in most applications and, more importantly, indispensable in many cases. Generally speaking, IR communication fulfills all previously exposed requirements for swarm robotics. Another distinction can be highlighted in the case of semantics. Essentially, we can differentiate between direct communication semantics and codes that are handcrafted by the researcher and communication semantics that arise from automatic controller design methods (e.g., ER). In the latter scenario, it is said that communication emerges. Clearly, the researcher still has to design and establish the communication means and resources, albeit the semantics and the information relevant to the emerged communication is a result from optimization processes. Within this context, the taxonomy previously described according to [24] can be reformulated as follows (see [29]):  
* _Abstract communication_: is a type of communication in which only the message content carries information. The environmental context associated to the message is either not processed or not relevant in the emerged communication. See e.g., [30; 31] and some of the experiments of [32]. * _Situated communication_: refers to communication scenarios in which both the message content and its corresponding environmental context carry information within the communication. Environmental context can be, for instance, the signal strength from which the distance can be estimated or the direction from where the message was received. Some examples of situated communication are [9; 33].