Science Mag - Tag Archive

Fighting spam and recapturing books with reCAPTCHA

2 Replies Christopher Roberts

A CAPTCHA is an anti-spam test used to work out whether a request has been made by a human, or a spambot. CAPTCHAs no longer seem to be as popular as they once were, as other spam identification techniques have emerged, however a considerable number of websites still use them.

CAPTCHA pictures

Some common examples of CAPTCHAs.

CAPTCHAs can be really annoying, hence their downfall in recent years. Take a look at the different CAPTCHAs in the image above, if you had spent 30 seconds filling in a feedback form, would you be willing to try and decipher one of the above CAPTCHAs, or would you just abandon the feedback?

The top left image could be ZYPEB, however it could just as easily be 2tPF8. If you get it wrong, usually you will be forced to do another, which could be just as difficult.

The BBC recently reported how The National Federation for the Blind has criticised CAPTCHAs, due to their restrictive nature for the visually impaired. Many CAPTCHAs do offer an auditory version, however if you check out the BBC article (which has an example of an auditory CAPTCHA), you will see that they are near impossible to understand.

reCAPTCHA

Luis von Ahn is a computer scientist who was instrumental in developing the CAPTCHA back in the late 90’s and early 2000’s. According to an article the Canadian magazine The Walrus, when CAPTCHAs started to become popular, Luis von Ahn “realized that he had unwittingly created a system that was frittering away, in ten-second increments, millions of hours of a most precious resource: human brain cycles.”

Anti-spam reCAPTCHA

An example of a reCAPTCHA CAPTCHA.

In order to try and ensure that this time was not wasted, von Ahn set about developing a way to better utilise this time; it was at this point that reCAPTCHA was born.

reCAPTCHA is different to most CAPTCHAs because it uses two words. One word is generated by a computer, whilst the other is taken from an old book, journal, or newspaper article.

Recapturing Literature

As I mentioned, reCAPTCHA shows you two words. One of the images is to prevent spam, and confirm the accuracy of your reading; you must get this one right, or you will be presented with another. The other image is designed to help piece together text from old literature, so that books, newspapers and journals can be digitised.

reCAPTCHA presents the same word to a variety of users and then uses the average response to work out what the word actually says – this helps to stop abuse. In a 2007 quality test, using a standard computer text reader, (also known as OCR) 83.5% of words were identified correctly – a reasonably high amount – however the accuracy of human interpretation via reCAPTCHA was an astonishing 99.1%!

According to an entry in the journal Science, in 2007 reCAPTCHA was present on over 40,000 websites, and users had interpreted over 440 million words! Google claim that today around 200 million CAPTCHAs are solved each day.

If each CAPTCHA took 10 seconds to solve, that would have been around 139 years (or 4.4 billion seconds) of brain time wasted; I am starting to see what Mr von Ahn meant! To put the 440 million words into perspective, the complete works of Shakespeare is around 900,000 words – or 0.9 million.

Whilst the progress of reCAPTCHA seems pretty impressive, it is a tiny step on the path to total digitisation. According to this BBC article, at the time von Ahn is quoted saying:

“There’s still about 100 million books to be digitised, which at the current rate will take us about 400 years to complete”

Google

In 2009 Google acquired reCAPTCHA. The search giant claimed that it wanted to “teach computers to read” hence the acquisition.

Many speculate that Google‘s ultimate aim is to index the world, and reCAPTCHA will help it to accelerate this process. That said, if that is its goal, it is still a very long way off.

We won’t be implementing a CAPTCHA on Technology Bloggers any time soon, however next time you have to fill one in, do spare a thought for the [free] work you might be doing for literature, for history and for Google.

Search engines are changing the way our memory works

17 Replies Christopher Roberts

A recent article in Science Mag suggests that the use of computers and the internet might actually be changing the way our memory works.

A series of psychology experiments recently carried out have shown that sometimes, when people were presented with hard to answer questions, they began to think of computers.

If participants believed that it would be easy to find answers on Google later, then they had poorer recall of the actual answer, and yet a greater memory of where the answer was stored.

A head x-ray showing someone with a computer for a brainThe researchers said that the internet acts as a tool which we now depend upon to to aid our memories, by remembering some data for us.

Here is the abstract for the journal entry

The advent of the Internet, with sophisticated algorithmic search engines, has made accessing information as easy as lifting a finger. No longer do we have to make costly efforts to find the things we want. We can “Google” the old classmate, find articles online, or look up the actor who was on the tip of our tongue. The results of four studies suggest that when faced with difficult questions, people are primed to think about computers and that when people expect to have future access to information, they have lower rates of recall of the information itself and enhanced recall instead for where to access it. The Internet has become a primary form of external or transactive memory, where information is stored collectively outside ourselves.

In more simplified English, what this is basically saying is that it is now much easier to access data online, mainly thanks to search engines like Google, Bing and Yahoo. If we have a question, we can find the answer in seconds.


This has lead the the human brain associating the thought of a problem with computers, as it believes that the internet will be the source of the solution. Search engines are now embeded so much in our brain, that when we think of a problem, we no longer bother trying to work out the answer for ourselves, but instead we associate the possibility of finding the solution of the problem with a search engine.

Let’s be honest, who hasn’t been bugged by something, asked someone else who also wasn’t able to help and as a result was either told “Google it” or thought “I could Google that”? I have, in fact I would say it happens on a weekly basis!

Question time

So what do you think? Are computers, the internet and search engines making us stupid, or is it just that we are now adapting as a race to more efficient ways of finding out information?