In 1996, computer scientist Moni Naor wrote an unpublished paper proposing 9 types of tests to filter bots from humans on the internet. His tests included everything from natural language processing (fill in the blank sentences) to visual recognition (circle the eye on a picture, deciding whether a photo is dressed or nude).
If only his suggestions had been implemented, the internet might be a much more interesting place today. Instead, the use of CAPTCHAs (those boxes of distorted text) has been widely incorporated by websites, in part due to their ease of implementation by programmers. But we have all been stymied at one time or another by distorted text, and bots have been advancing their ability to bypass these sorts of text processing tests. Ideally, it would be nice not to have any sort of hoops to jump through at all, and a number of non-interactive tests have been proposed. The “honeypot” defense, for instance, relies on the fact that bots navigate the web by viewing it through code. If you include a form field that is visually hidden to the human user, anyone filling in the hidden entry is most likely a bot.
The problem is that computers will eventually have the ability to perform all sorts of tasks in the future. As laid out in the classic Turing test, we want to measure whether an entity behaves like a human, rather than simply measuring ability. From Slate:
How might it be possible to measure behavior rather than ability? The other day, I was writing a note to company using the online form they provided for media requests, doing the usual amount of typing, backspacing, and retyping as I tried to phrase my note in a way that would make them respond quickly. It occurred to me that the random, circuitous way that people interact with Web pages—the scrolling and highlighting and typing and retyping—would be very difficult for a bot to mimic. A system that could capture the way humans interact with forms algorithmically could eventually relieve humans of the need to prove anything altogether.
I’m a Human, Computer, I Swear! [Slate]