PURPOSE: To learn new input-output relation while reducing adverse effects affected on already acquired proper input-output relation by preparing caution signals for restricting the range of an input part to be learned.

CONSTITUTION: An input/output device 4 for changing the input-output relation based upon a teacher signal 3 so as to generate a proper output in accordance with an input is provided with caution signals 5 for restricting the range of an input part to be learned. In a scene for practical pattern processing, a partial input 1 frequently has large influence on an output 2. When a caution signal 5 is applied only to a certain input part having influence on the output 2 in a certain input pattern, connection 8 unrelated to the output 2 is not changed, so that the effective connection acquired by preceding learning is not changed. Namely an unnecessary learning can be prevented and already stored information is held, so that learning efficiency can be improved.