Do you want to see naked celebrities? If you do, you may have become an unwitting worker in a distributed data-processing workforce.

CAPTCHAs are the boxes of distorted text that you are asked to identify when you enter data or register with some websites. There's an example on the left. The idea is that they prevent automated sign-ups and spamming because it is relatively easy for humans to identify the distorted letters, but beyond the capabilities of most software.

Rogue advertising is big business on the net, and CAPTCHAs have become a significant barrier for people who rely on spam to make a quick buck selling dodgy Viagra, penis enlargement pills or grey-market imports. One way of getting round such security measures would be to enlist large numbers of people who type in the solutions. This is where the naked naked celebrities come in.

According to news reports, porn sites have been set up which require the user to solve a CAPTCHA to view the content. The CAPTCHAs, of course, are taken from other websites, and every user who provides the correct answer in their bid to see naked flesh also opens a door for spammers to automatically register another account or post another advert.

In this context, humans become mechanised problem solvers trained to present the results of their mental effort in a standard format. The software sees human intelligence as just another subroutine.

This form of cognitive outsourcing has recently been taken further by leading online businesses such Amazon and Google, who, instead of recruiting human intelligence through deception, are paying people to perform tasks that would otherwise stretch cutting-edge artificial intelligence (AI) to the limit - such as choosing which words best describe a picture - key information for a photo database.

This is a task that computers are very bad at, as it requires not only the ability to identify objects, but also an understanding of the social world. 'Birthday' is an excellent keyword for a picture of children looking excitedly at a candle-topped cake. While a computer could feasibly identify the objects in the photo, divining social meaning is way beyond the scope of commercial AI. Humans, in contrast, find this trivial.

People are being used to plug gaps in the software, which is being used by other people to solve information problems. Increasingly, data is being processed over a hybrid human-digital network, suggesting an uncanny 21st century symbiosis.

Human cognition is becoming both a market force and a unit-based commodity, and this trend is set to continue as companies develop more efficient ways of interfacing the minds of willing workers with automated systems.

As the market value of this commodity increases, so will attempts to hijack moments of human cognition, as spammers are already doing with their CAPTCHA-laden porn sites.

While many reputable companies will inform their users of the underlying purpose, the data cowboys will just want you working, however they can motivate you and whether you understand what's involved or not.

Online games provide a perfect way of disguising lucrative problems as entertaining puzzles, while other work can be packaged into small chunks and put in the way of users wanting, well, almost anything, as long as they want it hard enough.

Advertisers have long battled for our attention, but a new generation of cognitive hijackers are attempting to deceive us into being momentary, but unwitting, employees.

Link to article on integration of artificial intelligence into web services.
Link to Wikipedia page on Amazon's 'Mechanical Turk' service.

UPDATE: I've discovered that the design of games to harness human intelligence is the research area of Luis von Ahn from Carnegie Mellon University. There's a Google video of a fantastic talk by him explaining how some of the more respectable software is developing to harness users' intelligence. Thanks jswolf19!