Accessibility and CAPTCHA tests

I failed a CAPTCHA test yesterday, which got me thinking and researching CAPTCHA accessibility. Most of us have taken a CAPTCHA test to sign up for different on-line services -- they are the forms where you enter the letters you see in a graphic. They are usually on a patterned background so that computer programs like 'bots and spiders cannot gain access to the site. The test I failed used a bit-mapped graphic with so much background "noise" (little dots) that I couldn't tell whether it was an "r" or a "7".

The CAPTCHA (Completely Automated Public Turing test to Tell Computers and Humans Apart) is used to discriminate between human users and automated software.
[Apologies: Blogger deletes all the text following the ACRONYM tag whenever I try to use it. I've given up for now. Any Blogger experts with solutions for me, please be in touch]

There is a market need to verify whether the user is a human. Right now, the common CAPTCHA tests only can verify sighted humans. Even sighted humans have difficulty with it -- people with color blindness have difficulty discriminating the letters from the background. People using zoom magnifiers may not be able to discriminate the pattern when the "noise" is magnified.

So how can these be made accessible? An ALT tag would give it away to the 'bots. As other researchers in robotics work to make their robots more visually capable, they are defeating the earlier, easily decoded patterns. The CAPTCHA experts retaliate with more complex patterns to stymie the 'bots. Hence the CAPTCHA I saw -- too tough for sighted humans. The visual CAPTCHA are probably a dead-end, doomed to endless warfare between competing technologies. The existing auditory CAPTCHA currently in use today have their own problems - requiring a sound card, not accessible to deaf-blind, and too hard to decipher.

Unsurprisingly, the W3C has been doing research on the techniques for accessible CAPTCHAs as part of the Web Accessibility Guidelines V. 2.0. They list a number of alternatives. No silver bullet, but a combination of techniques will help. Friday's blog from Matt May (Web Accessibility for W3C) posts the good news of a logic puzzle solution for WordPress by Eric Meyer of CSS fame.

I'm looking forward to seeing more on this issue.

For more information: http://www.w3.org/TR/turingtest/