1. A memory system adapted to model psychological functions of a brain by using an artificial neural network structure, comprising: a short-term memory neural network unit formed that temporarily stores input pattern vectors; and a long-term memory neural network unit formed on the basis of output vectors provided by the short-term memory neural network unit; wherein the long-term memory neural network unit includes hierarchical neural networks for ordinary outputs, formed by using the output vectors of the short-term memory neural network unit.