La accesibilidad de reCAPTCHA

El artículo reCAPTCHA Accessibility reVISTED analiza la accesibilidad de reCAPTCHA, el sistema de captcha de Google.

Las conclusiones son que tiene problemas y no es accesible:

1. People who are deaf-blind cannot complete the secondary CAPTCHA. Neither the visual nor audio CAPTCHA is accessible to them. The only hope for them is if they never have to proceed beyond the simple checkbox. The checkbox itself is accessible.
2. The secondary CAPTCHA is language and culture-specific. Take, for example, the visual CAPTCHA shown above which asks users to identify the sandwiches. Users must understand English well enough to understand the question, and they must be familiar with sandwiches. (And anyone who attended HighEdWeb 2015 knows that sandwich is not an indisputable concept).
3. Keyboard users with eyesight can't access the visual challenge. They can access the audio challenge, but how would they know to pursue that option? It's not at all intuitive, plus visible keyboard focus is dubious.