<$BlogRSDUrl$> Marcus P. Zillman, M.S., A.M.H.A. Author/Speaker/Consultant
Marcus P. Zillman, M.S., A.M.H.A. Author/Speaker/Consultant
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Sunday, August 10, 2003  

Model for Motivational Bias
http://www.dylan.org.uk/OptimismAISB.html

The evolution of optimism: An agent-based model of adaptive bias presented by Dylan Evans, Annerieke Heuvelink and Daniel Nettle.

This project is inspired by the phenomenon of 'motivational bias'. It shows how the principle of maximum expected utility (MEU), can - in certain types of environment - be outperformed by 'biased' decision rules.

In this model, three types of agent live in a 2D gridworld consisting of 441 (21 x 21) patches, each of which represents an 'opportunity'. Each opportunity has a probability of success (p, ranging from 0-1), a benefit for success (b, ranging from 0.0001 to 10 energy points) and a cost of failure (c, ranging from 0.0001 to 10 energy points).The colour of the patch is determined by the probability of success, with darker patches representing more difficult opportunities.

Agents have only one goal - to maximise their energy points. In other words, their utility function is a linear function of their energy level. Agents have some knowledge of the probability of success (p), the benefit for success (b), and the cost of failure (c), for each opportunity they face. Those c, b and p are properties of the patch they are on an that moment. The level of noise affecting the agents' knowledge of these values can be set by means of the sliders on the interface.

For a more detailed explanation of the model, download the PDF file of The evolution of optimism: a multi-agent based model of adaptive bias in human judgement, a paper first presented at the AISB'03 Symposium on Scientific Methods for the Analysis of Agent-Environment Interaction at the University of Wales, Aberystwyth, on 9 April 2003.

posted by Marcus Zillman | 9:16 AM
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