Modeling Human Understanding of Complex Intentional Action with a Bayesian Nonparametric Subgoal Model

Most human behaviors consist of multiple parts, steps, or subtasks. These structures guide our action planning and execution, but when we observe others, the latent structure of their actions is typically unobservable, and must be inferred in order to learn new skills by demonstration, or to assist others in completing their tasks. For example, an assistant who has learned the subgoal structure of a colleague's task can more rapidly recognize and support their actions as they unfold. Here we model how humans infer subgoals from observations of complex action sequences using a nonparametric Bayesian model, which assumes that observed actions are generated by approximately rational planning over unknown subgoal sequences. We test this model with a behavioral experiment in which humans observed different series of goal-directed actions, and inferred both the number and composition of the subgoal sequences associated with each goal. The Bayesian model predicts human subgoal inferences with high accuracy, and significantly better than several alternative models and straightforward heuristics. Motivated by this result, we simulate how learning and inference of subgoals can improve performance in an artificial user assistance task. The Bayesian model learns the correct subgoals from fewer observations, and better assists users by more rapidly and accurately inferring the goal of their actions than alternative approaches.Comment: Accepted at AAAI 1

Reviews

Martin Oliver (ed.), Innovation in the Evaluation of Learning Technology, London: University of North London, 1998. ISBN: 1–85377–256–9. Softback, 242 pages, £15.00

Modeling Human Ad Hoc Coordination

Whether in groups of humans or groups of computer agents, collaboration is most effective between individuals who have the ability to coordinate on a joint strategy for collective action. However, in general a rational actor will only intend to coordinate if that actor believes the other group members have the same intention. This circular dependence makes rational coordination difficult in uncertain environments if communication between actors is unreliable and no prior agreements have been made. An important normative question with regard to coordination in these ad hoc settings is therefore how one can come to believe that other actors will coordinate, and with regard to systems involving humans, an important empirical question is how humans arrive at these expectations. We introduce an exact algorithm for computing the infinitely recursive hierarchy of graded beliefs required for rational coordination in uncertain environments, and we introduce a novel mechanism for multiagent coordination that uses it. Our algorithm is valid in any environment with a finite state space, and extensions to certain countably infinite state spaces are likely possible. We test our mechanism for multiagent coordination as a model for human decisions in a simple coordination game using existing experimental data. We then explore via simulations whether modeling humans in this way may improve human-agent collaboration.Comment: AAAI 201

Full-scale measurement and analysis of train slipstreams and wakes. Part 1: Ensemble averages

This paper describes a series of extensive and unique full-scale measurements of the slipstreams of trains of various types that were carried out as part of the EU-sponsored AeroTRAIN project, together with the analysis of the experimental data. These experiments were carried out with the fundamental aim of seeking to reduce the complexity of the current technical specifications for interoperability (TSI) testing methodology. Experimental sites in Spain and Germany were used, for a range of different train types - high-speed single-unit trains, high-speed double-unit trains, conventional passenger units and locomotive/coach combinations. The data that was obtained was supplemented by other data from previous projects. The analysis primarily involved a study of the ensemble averages of the slipstream velocities, measured both at trackside and above platforms. The differences between the flows around different train types were elucidated, and the effect of platforms on slipstream behaviour described. A brief analysis of the effects of crosswinds on slipstream behaviour was also carried out. Through a detailed analysis of slipstream velocity components, the detailed nature of the flow around the nose and in the near wake of the train was investigated, again revealing differences in flow pattern between different trains. Significant similarity in the far wake flows was revealed. These fundamental results form the basis for the detailed discussion of the proposed TSI methodology that will be presented in Part 2 of this paper. Overall the results enable the nature of the flow field around trains to be understood in far greater detail than before, and also allow the developments of a revised TSI methodology which is more efficient than current practice. © IMechE 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav

Water Quality Impacts from Agricultural Land Use in Karst Drainage Basins of SW Kentucky and SW China

Karst regions are composed of soluble rock, often limestone, which leads to the formation of fissures, sinkholes, and water flow conduits such as caves. Pollutants in karst waters tend to be quickly directed and concentrated into these subsurface conduits. As a result of this and other factors, water resources are especially sensitive to contamination and pollution in karst areas. Pollutant concentrations going into karst subsurface fluvial systems are often very similar to the concentrations surfacing at outlets such as springs. Areas connected by karst conduit flows must be distinctly determined and special attention should be given to water quality impacts from land-use practices near conduit inputs. The climate which affects a certain karst area can also have different impacts on water resources considerations. In the temperate climate of southwest Kentucky precipitation is mostly evenly distributed throughout the year. Southwest China is affected by a monsoon climate with high precipitation in the spring to summer and drier conditions in other seasons. In the wet season large storm pulses can effectively transport contaminants to water sources resulting in unhealthy loads, while the dry seasons can be particularly severe in karst areas as water quickly drains to the subsurface, making water access a major hardship. Our research focuses on the seasonal differences that the climate of southwest China poses for water quality, including differences in pesticide concentrations between agricultural and residential areas hydrologically linked by karst conduits. In late 2007 the fluvial connections in a simple karst system near Chongqing were confirmed using dye tracing techniques. The concentration of pesticides in agricultural runoff going into and coming out of the subterranean stream studied were within safe limits. Results supported that there was a close relationship among concentrations of the pesticides glyphosate, chlorothalonil, and atrazine in the input and the output of the system. Taking into account the rapid and direct flows in the karst system, the concentrations of the pesticides found in the output was more similar to the input than would be expected in a surface stream. Analysis of hydrology data of the site will be required before further conclusions can be developed. The research was conducted in the spring and summer of 2007–2008 and funded by the U.S. Agency for International Development

Multilingual Animacy Classification by Sparse Logistic Regression

This paper presents results from three experiments on automatic animacy classification in Japanese and English. We present experiments that focus on solutions to the problem of reliably classifying a large set of infrequent items using a small number of automatically extracted features. We labeled a set of Japanese nouns as ±animate on the basis of reliable, surface-obvious morphological features, producing an accurately but sparsely labeled data set. To classify these nouns, and to achieve good generalization to other nouns for which we do not have labels, we used feature vectors based on frequency counts of verbargument relations that abstract away from item identity and into class-wide distributional tendencies of the feature set. Grouping items into suffix-based equivalence classes prior to classification increased data coverage and improved classification accuracy. For the items that occur at least once with our feature set, we obtained 95% classification accuracy. We used loanwords to transfer automatically acquired labels from English to classify items that are zerofrequency in the Japanese data set, giving increased precision on inanimate items and increased recall on animate items

TARUC: A Topology-Aware Resource Utility and Contention Benchmark

Computer architects have increased hardware parallelism and power efficiency by integrating massively parallel hardware accelerators (coprocessors) into compute systems. Many modern HPC clusters now consist of multi-CPU nodes along with additional hardware accelerators in the form of graphics processing units (GPUs). Each CPU and GPU is integrated with system memory via communication links (QPI and PCIe) and multi-channel memory controllers. The increasing density of these heterogeneous computing systems has resulted in complex performance phenomena including nonuniform memory access (NUMA) and resource contention that make application performance hard to predict and tune. This paper presents the Topology Aware Resource Usability and Contention (TARUC) benchmark. TARUC is a modular, open-source, and highly configurable benchmark useful for profiling dense heterogeneous systems to provide insight for developers who wish to tune application codes for specific systems. Analysis of TARUC performance profiles from a multi-CPU, multi-GPU system is also presented

Rapid change in mammalian eye shape is explained by activity pattern

The rate of morphological evolution along the branches of a phylogeny varies widely [1-6]. Although such rate variation is often assumed to reflect the strength of historical natural selection resulting in adaptation [7-14], this lacks empirical and analytical evidence. One way to demonstrate a relationship between branchwise rates and adaptation would be to show that rapid rates of evolution are linked with ecological shifts or key innovations. Here we test for this link by determining whether activity pattern – the time of day at which species are active – explains rapid bursts of evolutionary change in eye shape. Using modern approaches to identify shifts in the rate of morphological evolution [7, 13], we find that over 74% of rapid eye shape change during mammalian evolutionary history is directly explained by distinct selection pressures acting on nocturnal, cathemeral, and diurnal species. Our results reveal how ecological changes occurring along the branches of a phylogeny can manifest in subsequent changes in the rate of morphological evolution. Although selective pressures exerted by different activity patterns have acted uniformly across all mammals, we find differences in the rate of eye shape evolution among orders. The key to understanding this is in how ecology itself has evolved. We find heterogeneity in how activity pattern has evolved among mammals that ultimately led to differences in the rate of eye shape evolution among species. Our approach represents an exciting new way to pinpoint factors driving adaptation, enabling a clearer understanding of what factors drive the evolution of biological diversity