CAPTCHA and Symbiotic Interaction

This chapter describes the CAPTCHA interfaces under the usability perspective, which is related to the interaction of the humans to the test. In particular, this interaction is connected to the efficiency aspect of the usability. This concerns the analysis of the solving time, also called response time, of different types of CAPTCHA by different users with specific personal and demographic characteristics. The dependence of the response time to CAPTCHA on the different user’s characteristics is explored by statistical analysis with the formulation of meaningful hypotheses which should be (dis)proved. Then, more complex patterns describing the dependence of the response time on the co-occurrence of different user’s characteristics are extracted by employing advanced statistical analysis. This is accomplished by using association rule mining on the collected users’ data.