PURPOSE: To attain a rejecting operation based on a correct standard and to assure the safety of an information processing system.

CONSTITUTION: A rejection mechanism 6 decides to reject the conditional probability calculated at a conditional. probability calculation part 3 based on the estimated value R of an error calculated at an estimated error calculation part 5. In other words, the conditional probability of the output (y) obtained to the unlearnt input (x) is rejected if the value R of the conditional probability is larger than a prescribed constant against the input (x).