The motivation and development of this expression for category utility, and the role of the multiplicand formula_14 as a crude overfitting control, is given in the above sources. Loosely , the term formula_15 is the expected number of attribute values that can be correctly guessed by an observer using a probability-matching strategy together with knowledge of the category labels, while formula_16 is the expected number of attribute values that can be correctly guessed by an observer the same strategy but without any knowledge of the category labels. Their difference therefore reflects the relative advantage accruing to the observer by having knowledge of the category structure.