Using the Winograd Schema Challenge as a CAPTCHA

CAPTCHAs have established themselves as a standard technology to confidently distinguish humans from bots. Beyond the typical use for security reasons, CAPTCHAs have helped promote AI research in challenge tasks such as image classification and optical character recognition. It is, therefore, natural to consider what other challenge tasks for AI could serve a role in CAPTCHAs. The Winograd Schema Challenge (WSC), a certain form of hard pronoun resolution tasks, was proposed by Levesque as such a challenge task to promote research in AI. Based on current reports in the literature, the WSC remains a challenging task for bots, and is, therefore, a candidate to serve as a form of CAPTCHA. In this work we investigate whether this a priori appropriateness of the WSC as a form of CAPTCHA can be justified in terms of its acceptability by the human users in relation to existing CAPTCHA tasks. Our empirical study involved a total of 329 students, aged between 11 and 15, and showed that the WSC is generally faster and easier to solve than, and equally entertaining with, the most typical existing CAPTCHA tasks.