Factorial Learning and the EM Algorithm

Zoubin Ghahramani, Dept. of Brain & Cognitive Sciences,
Massachusetts Institute of Technology, Cambridge, MA 02139

Many real world learning problems are best characterized by an interaction of multiple independent causes or factors. Discovering such causal structure from the data is the focus of this paper. Based on Zemel and Hinton's cooperative vector quantizer (CVQ) architecture, an unsupervised learning algorithm is derived from the Expectation--Maximization (EM) framework. Due to the combinatorial nature of the data generation process, the exact E-step is computationally intractable. Two alternative methods for computing the E-step are proposed: Gibbs sampling and mean-field approximation, and some promising empirical results are presented.

In G. Tesauro, D.S. Touretzky, and J. Alspector (eds.), Advances in Neural Information Processing Systems 7. Morgan Kaufmann Publishers, San Francisco, CA, 1995. postscript.

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