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Andy Stewart

Senior Engineer

Email

andy@apl.washington.edu

Phone

206-221-8015

Biosketch

Andrew Stewart's research supports the development of next-generation ocean science technology and the creation of new tools to improve robotic exploration of marine environments. Stewart's interests include dynamics and automated control of mechanical systems, decision-making dynamics in mixed teams of humans and robots, and development of deployable hardware for exploration of remote environments. Stewart contributes to all phases of development from conceptual design to prototype fabrication and testing. He has worked to develop a number of mobile sensor platforms, including unmanned air vehicles and autonomous underwater vehicles. Through employing control theoretic tools and design methodologies rooted in fundamental principles, Stewart aims to extend the limits of human presence in the ocean.

Department Affiliation

Ocean Engineering

Education

B.S. Mechanical Engineering, University of California San Diego, 2006

M.A. Dynamics & Control Theory, Princeton University, 2008

Ph.D. Mechanical & Aerospace Engineering, Princeton University, 2011

Publications

2000-present and while at APL-UW

Towards human–robot teams: Model-based analysis of human decision making in two-alternative choice tasks with social feedback

Stewart, A., M. Cao, A. Nedic, D. Tomlin, and N. Leonard, "Towards human–robot teams: Model-based analysis of human decision making in two-alternative choice tasks with social feedback," Proc. IEEE, 100, 751-775, doi:10.1109/JPROC.2011.2173815, 2012.

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1 Mar 2012

With a principled methodology for systematic design of human–robot decision-making teams as a motivating goal, we seek an analytic, model-based description of the influence of team and network design parameters on decision-making performance. Given that there are few reliably predictive models of human decision making, we consider the relatively well-understood two-alternative choice tasks from cognitive psychology, where individuals make sequential decisions with limited information, and we study a stochastic decision-making model, which has been successfully fitted to human behavioral and neural data for a range of such tasks. We use an extension of the model, fitted to experimental data from groups of humans performing the same task simultaneously and receiving feedback on the choices of others in the group. First, we show how the task and model can be regarded as a Markov process. Then, we derive analytically the steady-state probability distributions for decisions and performance as a function of model and design parameters such as the strength and path of the social feedback. Finally, we discuss application to human–robot team and network design and next steps with a multirobot testbed.

The role of social feedback in steady-state performance of human decision making for two-alternative choice tasks

Stewart, A., and N.E. Leonard, "The role of social feedback in steady-state performance of human decision making for two-alternative choice tasks," in Proc., 49th IEEE Conf. Decision and Control, 15-17 December, Atlanta, GA, 3796-3801, doi:10.1109/CDC.2010.5717531 (IEEE, 2010).

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15 Dec 2010

With an eye towards design of human-in-the-loop systems, we investigate human decision making in a social context for tasks that require the human to make repeated choices among finite alternatives. We consider a human decision maker who receives feedback on his/her own performance as well as on the choices of others performing the same task. We use a drift-diffusion, decision-making model that has been fitted to human neural and behavioral data in sequential, two-alternative, forced-choice tasks and recently extended to the social context with an empirically derived feedback term that depends on choices of other decision makers.

We show conditions for this model to be a Markov process, and we derive the steady-state probability distribution for choice sequences and individual performance as a function of the strength of the social feedback. It has recently been shown in behavioral experiments that human decision-making performance for a relatively easy task is decreased with this social feedback; we show that our analytic predictions agree with this finding.

Steady-state distributions for human decisions in two-alternative choice tasks

Stewart, A., M. Cao, and N.E. Leonard, "Steady-state distributions for human decisions in two-alternative choice tasks," in Proc., American Control Conference, 30 June - 2 July, Baltimore, MD, 2378-2383 (IEEE, 2010).

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30 Jun 2010

In human-in-the-loop systems, humans are often faced with making repeated choices among finite alternatives in response to observations of the evolving system performance. In order to design humans into such systems, it is important to develop a systematic description of human decision making in this context. We examine a commonly used, drift-diffusion, decision-making model that has been fit to human neural and behavioral data in sequential, two-alternative, forced-choice tasks.

We show how this model and type of task together can be regarded as a Markov process, and we derive the steady-state probability distribution for choice sequences. Using the analytic expression for this distribution, we prove matching behavior for tasks that exhibit a matching point and we compute the sensitivity of steady-state choices to a model parameter that measures the decision maker's "exploratory" tendency.

More Publications

Convergence in human decision-making dynamics

Cao, M., A. Stewart, and N.E. Leonard, "Convergence in human decision-making dynamics," Syst. Control Lett., 59, 87-97, doi:10.1016/j.sysconle.2009.12.00, 2010.

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1 Feb 2010

A class of binary decision-making tasks called the two-alternative forced-choice task has been used extensively in psychology and behavioral economics experiments to investigate human decision making. The human subject makes a choice between two options at regular time intervals and receives a reward after each choice; for a variety of reward structures, these experiments show convergence of the aggregate behavior to rewards that are often suboptimal.

In this paper we present two models of human decision making: one is the Win-Stay, Lose-Switch (WSLS) model and the other is a deterministic limit of the popular Drift Diffusion (DD) model. With these models we prove the convergence of human behavior to the observed aggregate decision making for reward structures with matching points. The analysis is motivated by human-in-the-loop systems, where humans are often required to make repeated choices among finite alternatives in response to evolving system performance measures. We discuss application of the convergence result to the design of human-in-the-loop systems using a map from the human subject to a human supervisor.

Integrating human and robot decision-making dynamics with feedback: Models and convergence analysis

Cao, M., A. Stewart, and N.E. Leonard, "Integrating human and robot decision-making dynamics with feedback: Models and convergence analysis," in Proc., 47th Conf. Decision and Control, 9-11 December, Cancun, Mexico, 1127-1132, doi:10.1109/CDC.2008.4739103 (IEEE, 2008).

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9 Dec 2008

Leveraging research by psychologists on human decision-making, we present a human-robot decision-making problem associated with a complex task and study the corresponding joint decision-making dynamics. The collaborative task is designed so that the human makes decisions just as human subjects make decisions in the two-alternative, forced-choice task, a well-studied decision-making task in behavioral experiments. The human subject chooses between two options at regular time intervals and receives a reward after each choice; for a variety of reward structures, the behavioral experiments show convergence to suboptimal choices.

We propose a human-supervised robot foraging problem in which the human supervisor makes a sequence of binary decisions to assign the role of each robot in a group in response to a report from the robots on their resource return. We discuss conditions under which the decision dynamics of this human-robot task is reasonably well approximated by the kinds of reward structures studied in the psychology experiments. Using the win-stay, lose-switch human decision-making model, we prove convergence to the experimentally observed aggregate human decision-making behavior for reward structures with matching points. Finally, we propose an adaptive law for robot reward feedback designed to help the human make optimal decisions.

Inventions

Methods for Underwater Haptic Rendering Using Non-contact Sensors

Record of Invention Number: 46396

Wei-Chih Wang, Fredrik Ryden, Payman Arabshahi, Andy Stewart, Howard Chizeck

Disclosure

7 Feb 2013

Virtual Fixtures for Subsea Technology

Record of Invention Number: 46397

Andy Stewart, Fredrik Ryden, Howard Chizeck

Disclosure

7 Feb 2013

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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