The inductive bias (also known as learning bias) of a learning algorithm is the set of assumptions that the learner uses to predict outputs of given inputs that it has not encountered.[1]

In machine learning, one aims to construct algorithms that are able to learn to predict a certain target output. To achieve this, the learning algorithm is presented some training examples that demonstrate the intended relation of input and output values. Then the learner is supposed to approximate the correct output, even for examples that have not been shown during training. Without any additional assumptions, this problem cannot be solved since unseen situations might have an arbitrary output value. The kind of necessary assumptions about the nature of the target function are subsumed in the phrase inductive bias.[1][2]

A classical example of an inductive bias is Occam's razor, assuming that the simplest consistent hypothesis about the target function is actually the best. Here consistent means that the hypothesis of the learner yields correct outputs for all of the examples that have been given to the algorithm.

Approaches to a more formal definition of inductive bias are based on mathematical logic. Here, the inductive bias is a logical formula that, together with the training data, logically entails the hypothesis generated by the learner. However, this strict formalism fails in many practical cases, where the inductive bias can only be given as a rough description (e.g. in the case of artificial neural networks), or not at all.

Types

The following is a list of common inductive biases in machine learning algorithms.

Shift of bias

Although most learning algorithms have a static bias, some algorithms are designed to shift their bias as they acquire more data.[3] This does not avoid bias, since the bias shifting process itself must have a bias.

See also

References

  1. ^ a b Mitchell, T. M. (1980), The need for biases in learning generalizations, CBM-TR 5-110, New Brunswick, New Jersey, USA: Rutgers University, CiteSeerX 10.1.1.19.5466
  2. ^ DesJardins, M.; Gordon, D. F. (1995), Evaluation and selection of biases in machine learning, Machine Learning Journal, vol. 5:1--17
  3. ^ Utgoff, P. E. (1984), Shift of bias for inductive concept learning, New Brunswick, New Jersey, USA: Doctoral dissertation, Department of Computer Science, Rutgers University, ISBN 9780934613002