Evaluating the usability of CAPTCHAs on a mobile device with voice and touch input

Abstract

The usability of text-based CAPTCHAs, featuring distorted letters, and image-based CAPTCHAs, featuring pictures, was explored on an Apple iPad. Five conditions were explored: Confident CAPTCHA with either voice or touch input, ESP-PIX with voice or touch input, and Google’s CAPTCHA with touch input. Usability was analyzed in terms of performance, perceived usability, workload, and preference rankings. Results showed that CAPTCHAs involving touch input scored better in almost every measure than CAPTCHAs involving voice input. In particular, Confident Touch is recommended based on preference and perceived performance, whereas ESP-PIX Touch is recommended for its short completion time. When image-based CAPTCHAs are not feasible, Google’s CAPTCHA is a satisfactory alternative based on usability ratings.