Robots communicating with fish: Investigating the role of electric signals and locomotor displays following episodes of mutual attention in weakly electric fish

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Animals that live in social groups must interact in order to stay together and move collectively. A fundamental biological question is which rules govern social interactions and cause group members to coordinate their movements and come to joint decisions. In fish shoals, individuals exchange information through different sensory channels, e.g. through vision or the mechanosensory lateral line system. In previous studies, we have shown that mormyrid weakly electric fish rely almost exclusively on their electro-sensory modality for group coherence and shoal formation. Individuals emit and perceive electric signals to localize and approach conspecifics within the group, and even fully accept an artificial, bodiless signal source as communication partner. Besides emitting context-specific signal patterns, shoaling mormyrids frequently engage in episodes of interactive electric signalling by synchronizing their signals to each other. However, it is not yet known which signals are actually exchanged via this channel, what these signals mean and which behaviour they evoke in other fish.In this project, we want to investigate the basic processes that support social interactions in shoals of weakly electric fish by developing a biomimetic electric fish robot that serves as communication partner in a group. By designing a fully interactive robot, which operates in closed-loop both electrically and locomotory, we will have full control over the cues we inject into the social system.One of our main goals is to understand why two group members often synchronize their signals when they approach each other. We will test the hypothesis that this behaviour is a strategy to address another individual in the group and to provoke "social attention" - i.e., a means for two animals to open an exclusive communication channel through which information can be exchanged, expressed by the behaviour that follows the electrical synchronization.By introducing a fully interactive robot into the group, which is able to establish and sustain mutual synchronization episodes between fish and robot, we will investigate the effect of ensuing locomotor and/or electrical interactions on the behaviour of the fish. The robot’s behaviour will be based on an analysis of post-sync behaviours in all-fish groups in order to find out what happens during and immediately after two fish have synchronized, and which actions can transmit information to another individual. By extracting behavioural properties at the level of the individual and the group, we will assess differences between fully interactive robot behaviours and behaviours that lack either the electrical or the locomotor interactive component, respectively. The robot’s effectiveness to alter the behaviour of single fish and the whole group will be assessed by employing modern statistical methods to quantify information transfer between individuals.