Computer Science Department
School of Computer Science, Carnegie Mellon University


Multitask Learning

Rich Caruana

September 1997

Ph.D. Thesis

Keywords: Machine learning, neural networks, k-nearest neighbor, multitask learning, inductive bias, medical decision making, pneumonia, ALVINN, autonomous vehicle navigation, pattern recognition, inductive transfer, learning-to-learn

Multitask Learning is an approach to inductive transfer that improves learning for one task by using the information contained in the training signals of other related tasks. It does this by learning tasks in parallel while using a shared representation; what is learned for each task can help other tasks be learned better. In this thesis we demonstrate multitask learning for a dozen problems. We explain how multitask learning works and show that there are many opportunities for multitask learning in real domains. We show that in some cases features that would normally be used as inputs work better if used as multitask outputs instead. We present suggestions for how to get the most out of multitask learning in artificial neural nets, present an algorithm for multitask learning with case-based methods like k-nearest neighbor and kernel regression, and sketch an algorithm for multitask learning in decision trees. Multitask learning improves generalization performance, can be applied in many different kinds of domains, and can be used with different learning algorithms. We conjecture there will be many opportunities for its use on real-world problems. 255 pages

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