CAPTCHA is a technique that is used to prevent automatic programs from being able to acquire free e-mail or online service accounts. However, as many researchers have already reported, conventional CAPTCHA could be overcome by state-of-the-art malware since the capabilities of computers are approaching those of humans. Therefore, CAPTCHA should be based on even more advanced human-cognitive-processing abilities. In addition, it is also important to keep in mind that answering CAPTCHA is an added annoyance for users, who feel troublesome to prove that they are human at every Web access. So, CAPTCHA should be enjoyable for users. To cope with these issues, this paper focuses on using the human ability to understand humor, which represents the ultimate in human cognitive processing abilities, and propose a new CAPTCHA that uses four-panel cartoons.
