Homeostatic plasticity improves signal propagation in continuous time recurrent neural networks

Continuous-time recurrent neural networks (CTRNNs) are potentially an excellent substrate for the generation of adaptive behaviour in artificial autonomous agents. However, node saturation effects in these networks can leave them insensitive to input and stop signals from propagating. Node saturation is related to the problems of hyper-excitation and quiescence in biological nervous systems, which are thought to be avoided through the existence of homeostatic plastic mechanisms. Analogous mechanisms are here implemented in a variety of CTRNN architectures and are shown to increase node sensitivity and improve signal propagation, with implications for robotics. These results lend support to the view that homeostatic plasticity may prevent quiescence and hyper-excitation in biological nervous systems

Social learning in a multi-agent system

In a persistent multi-agent system, it should be possible for new agents to benefit from the accumulated learning of more experienced agents. Parallel reasoning can be applied to the case of newborn animals, and thus the biological literature on social learning may aid in the construction of effective multi-agent systems. Biologists have looked at both the functions of social learning and the mechanisms that enable it. Many researchers have focused on the cognitively complex mechanism of imitation; we will also consider a range of simpler mechanisms that could more easily be implemented in robotic or software agents. Research in artificial life shows that complex global phenomena can arise from simple local rules. Similarly, complex information sharing at the system level may result from quite simple individual learning rules. We demonstrate in simulation that simple mechanisms can outperform imitation in a multi-agent system, and that the effectiveness of any social learning strategy will depend on the agents' environment. Our simple mechanisms have obvious advantages in terms of robustness and design costs

Task allocation in dynamic networks of satellites

The management of distributed satellite systems requires the coordination of a large number of heterogeneous spacecraft. Task allocation in such a system is complicated by limited communication and individual satellite dynamics. Previous work has shown that task allocation using a market-based mechanism can provide scalable and efficient management of static networks; in this paper we extend this work to determine the impact of dynamic topologies. We develop a Keplerian mobility model to describe the topology of the communication network over time. This movement model is then used in simulation to show that the task allocation mechanism does not show a significant decrease in effectiveness from the static case, reflecting the suitability distributed market-based control to the highly dynamic environment

An agent-based model of jaguar movement through conservation corridors

Wildlife corridors mitigate against habitat fragmentation by connecting otherwise isolated regions, bringing well established benefits to conservation both in principle and practice. Populations of large mammals in particular may depend on habitat connectivity, yet conservation managers struggle to optimise corridor designs with the rudimentary information generally available on movement behaviours. We present an agent-based model of jaguars (Panthera onca), scaled for fragmented habitat in Belize where proposals already exist for creating a jaguar corridor. We use a leastcost approach to simulate movement paths through alternative possible landscapes. Six different types of corridor and three control conditions differ substantially in their effectiveness at mixing agents across the environment despite relatively little difference in individual welfare. Our best estimates of jaguar movement behaviours suggest that a set of five narrow corridors may out-perform one wide corridor of the same overall area. We discuss the utility of ALife modelling for conservation management

Simulating bounded rationality: Optimality modelling without an optimality commitment

If you accept that evolved agents will be only boundedly rational, what are the consequences for the tools we use to make models of and construct theories about behaviour? In particular, consider methods like agent-based modelling -- with its roots in game theory and incorporating a notion of optimization or maximizing across alternatives -- do such methods remain viable? Or can cognitive science only deal with contingent, historical accounts of behaviour? I will argue that optimality models can continue to be used, because when used properly they were never wedded to a global notion of optimization or rationality in the first place. Such models are best viewed as ways of finding out which of a pre-specified set of behavioural alternatives is likely to dominate in a specific environment. As such, they are important tools for a program of research into bounded rationality. The argument will be illustrated with examples from modelling work on social learning in rats and intentional communication in monkeys

Value Stream Improvements using Kanban for the X-Workcell

A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Jason Noble on August 26, 2003

Distributed and Centralized Task Allocation: When and Where to Use Them

Self-organisation is frequently advocated as the solution for managing large, dynamic systems. Distributed algorithms are implicitly designed for infinitely large problems, while small systems are regarded as being controllable using traditional, centralised approaches. Many real-world systems, however, do not fit conveniently into these "small" or "large" categories, resulting in a range of cases where the optimal solution is ambiguous. This difficulty is exacerbated by enthusiasts of either approach constructing problems that suit their preferred control architecture. We address this ambiguity by building an abstract model of task allocation in a community of specialised agents. We are inspired by the problem of work distribution in distributed satellite systems, but the model is also relevant to the resource allocation problems in distributed robotics, autonomic computing and wireless sensor networks. We compare the behaviour of a self-organising, market-based task allocation strategy to a classical approach that uses a central controller with global knowledge. The objective is not to prove one mechanism inherently superior to the other; instead we are interested in the regions of problem space where each of them dominates. Simulation is used to explore the trade-off between energy consumption and robustness in a system of intermediate size, with fixed communication costs and varying rates of component failure. We identify boundaries between regions in the parameter space where one or the other architecture will be favoured. This allows us to derive guidelines for system designers, thus contributing to the development of a disciplined approach to controlling distributed systems using self-organising mechanisms

Under the Thumb : The Role of SMS in the Forming and Maintenance of Adolescent Dating Relationships

The use of the mobile phone is a ubiquitous feature of many an individual\u27s social life within contemporary society. Given this, it is somewhat surprising that little academic research has been undertaken into its effects on the social and cultural lives of key user populations. In particular, the Short Message Service- SMS texting- is a mobile phone application that has transformed the lives of large numbers of adolescent city dwellers. Moreover, teenagers and young adults, who represent the adolescent population, have adopted this mobile phone application and subsequently applied it to their social lives in ways that never would have been envisaged when it was first invented. Specifically, the coupling of the portability of the mobile phone and text-based SMS Messaging has resulted in the co-present sharing of the mobile phone and its contents with strangers or the familiar friendship circle as part of \u27making a connection\u27. SMS messaging is increasingly playing a role in the forming and maintenance of relationships. In particular, this communication technology supports a crucial preoccupation of adolescents, which is the fanning of both dating and friendship liaisons. This thesis seeks to investigate the role SMS plays in the forming and maintenance of adolescent dating relationships, and also addresses elements of its role in relation to friendship networks

Artificial life: Discipline or method? Report on a debate held at ECAL99

How can artificial life (AL) advance scientific understanding? Is AL best seen as a new discipline, or as a collection of novel computational methods that can be applied to old problems? And given that the products of AL research range from abstract existence proofs to working robots to detailed simulation models, are there standards of quality or usefulness that can be applied across the whole field? On September 16th, 1999 in Lausanne, Switzerland, a debate on these questions was held as part of the Fifth European Conference on Artificial Life. As the organizers, we wanted to foster a constructive discussion regarding the scientific status, and future, of AL. We were well aware that some of these issues had been raised before (e.g., Miller [2]) but we felt that earlier treatments had perhaps not reached a wide enough audience. The format for the debate consisted of contributions from invited panelists followed by an open discussion. The panelists were Chris Langton, Mark Bedau, Simon Kirby, and Inman Harvey—Hiroaki Kitano was scheduled to participate but regrettably could not attend the conference