A few months back, I wrote the post, A Quick Look at How the Human Brain Works. This post looks at a specific example of how computers use our particular ways of thinking for practical, everyday purpose.
We all have all been asked to type in the letters and numbers in those funky word pictures on websites. These pictures are called CAPTCHAs and are used to identify whether a website visitor is human or computer. Online banks, stores, news sites, chat boards and other sites want to weed out automated programs that try to steal information and spam message boards.
The question you may have is how do these pictures identify a user as human.
CAPTCHAs are designed around human shape and pattern biases, and the natural human ability to guess at or pick out identities in ambiguous information.
The letters and numbers in the CAPTCHAs are not the letters and numbers, but abbreviated, mixed-up, distorted versions. There is often other information (visual noise) overlapping and/or surrounding it. As in the above and below pictured CAPTCHAs, there usually is no separation between the letters and numbers, and the graphic can only be imagined as separate symbols.
When told to pick out the symbols, the human picks out which letters and numbers they perceive. The symbols do not match the textbook letters and numbers, but the human guesses what they most approximate. Those ‘pick which image contains a boat (or bicycle, traffic light, etc.)?’ tests work on the same theory, with none of the pictures showing the entire object.
Computers can eventually, or at least sometimes, identify the symbols but it takes longer. They have more difficulty with the ambiguous, messy, and mixed-up images.
What is especially interesting about this is that CAPTCHAs use the human’s ability to misperceive, or perceive what isn’t there, for practical use.