In his theory, human laughter is produced in four successive emotional stages -- letting loose, then deviating from the norm, followed by freely laughing and then having the laughter overflow.

• 木村教授自信地说：“我认为人脑中存在一个回路，能通过以上这几个步骤产生笑声。了解这一机制有助于我们解开人类自身的一大秘密。”