Last weekend, one of the nystagmus.co.uk forum‘s main contributors, Larry, started a topic entitled ‘Spam sandwich‘. The topic discusses some of the spam issues we have been experiencing behind the scenes on the forum. On most websites that allow users to register or make posts, you will almost certainly be faced with a CAPTCHA.
CAPTCHA – Completely Automatic Public Turing test to tell Computers and Humans Apart
For those that don’t know, the most common CAPTCHA is generally a computer generated series of letters and numbers, which are frequently distorted in order to prevent ’spam bots‘ from accessing forums and other interactive services. Sadly, for most people with nystagmus (and other visually impaired surfers), they make it impossible to register on some websites!
Whilst reading about CAPTCHA techniques, I found a very disappointing example – one where the user is asked to trace around a silhouette in an image. Here is an example. I tried this and failed 2 out of 4 attempts. Something tells me that it’s not just the visually impaired that would find this difficult. One user group that developers often forget about is those with cognitive disabilities.
Fortunately, some web developers have thought about the visually impaired. reCAPTCHA is such a considerate project. Whilst the style of CAPTCHA is the traditional one, it provides an audio version of it, thus allowing even blind users the ability to pass the challenge. This is still not an ideal solution.
As the the acronym suggests, CAPTCHAs do not necessarily need to be an exercise of trying to decipher the characters in a distorted image or indeed enter characters named in an audio file. A CAPTCHA could be as simple as asking a relatively simple question, like ‘How many eyes do humans have?‘. The problem comes with composing the questions because our forum employs this type of CAPTCHA and spambots still manage to register by the dozen!
Question and answer style CAPTCHAs are a great solution; they are accessible. The questions need to be composed to ensure that the range of answers are kept to a minimum. Questions need to be such that 99% of users will respond with the same answer. Preferably, answers should not be numbers and kept to a single word. It’s difficult.
At the end of the day, CAPTCHAs exist to enhance the user experience by maintaining a friendly environment, however, for some users, they can achieve quite the opposite!
If you have any ideas for suitable challenge question and answer sets, please contribute them to the ‘Spam sandwich‘ forum topic.