1. An information processing apparatus which creates a feature detection algorithm for detecting features from content data, said information processing apparatus comprising: low-level feature extraction expression list creation means for creating next-generation expression lists each constituted by a plurality of low-level feature extraction expressions through learning based on latest-generation expression lists, said low-level feature extraction expressions being expressions to which either said content data or metadata corresponding to said content data is input and from which low-level features are output; computation means for computing said low-level features using said next-generation expression lists created by said low-level feature extraction expression list creation means; and high-level feature extraction expression creation means for creating high-level feature extraction expressions through learning based on training data constituted by previously furnished true high-level features corresponding to said content data, said high-level feature extraction expressions being expressions to which said low-level features computed by said computation means are input and from which high-level features characteristic of said content data are output, wherein the learning comprises: bisecting the training data into learning data and evaluation data, evaluating the results of the learning using the relevant evaluation data, performing a cross-validation loop, selecting the most highly-evaluated result of the cross-validation loop, performing an algorithm loop, selecting the most highly-evaluated result of the algorithm loop, performing a training data loop, and performing a list loop.