CAPTCHAs – Maybe I’m not human

CAPTCHA - image of android robot with the CAPTCHA checkbox

Turing test: A test of a machine’s ability to exhibit intelligent behaviour that cannot be distinguished from that of a human.

Does a CAPTCHA ever make you want to pull out your hair? There are some that make me wonder if I’ve failed the test of being human.


The word CAPTCHA is an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”. You might not have heard that before. Wikipedia aptly describes it as a contrived acronym.

As you know, the purpose of a CAPTCHA is to check if a user is human by using a challenge–response test. The test itself is fully automated. That’s why it’s also sometimes called a reverse Turing test. In a Turing test, a human must determine if the “thing” answering the questions is human or machine. In a CAPTCHA test, a machine must determine the same thing.

CAPTCHAs that make me feel stupid

We’re all familiar with text-based CAPTCHAs. These have numbers and letters in strange fonts with a distorted perspective.

I don’t mind these too much. But there are times when I cannot figure out whether the character is an upper-case “O” or the number 0. Or the lower-case letter “l” or the number 1. And when the letters are random sizes, how can I know if it is an upper-case or lower-case letter “S”?

I do prefer text-based CAPCHAs over the Google Street View image versions. Am I the only one who wonders if that small part of a side mirror in the photo belongs to a motorcycle or a car or a taxi? And is there a minimum amount of a taxi that should be in the photo before I choose it?

I prefer MAPTCHAS (the “M” is for “Mathematical”) to either text or image-based versions. These ask you to do a simple calculation, like “12 + 5”. They are much quicker for me. But I’ve watched a small shopkeeper use a calculator to work out the change to give me – I gave her a R100 note for a R90 repair. (That says way too much about the failure of our schools to teach very, very basic maths.)

Is that a weird question?

As a user, I like the single checkbox CAPTCHA. That’s the one where the checkbox appears next to the words “I’m not a robot”. (I’ve used that in the blog post image, in case you can’t remember it.)

I wonder what most users think about that. Does it seem like a stupid question? It reminds me of applying for a visa to visit America. One of the questions is: “Do you plan to engage in terrorist activities while in the US?” If I was, would I answer yes?  Am I the only one who is amused at being asked if I’m a robot? 

The software is actually quite clever. It evaluates the movement of your cursor as you move your mouse towards the checkbox. Human motion has a degree of randomness on the microscopic level that bots can’t easily mimic. If the system isn’t convinced of your humanity, it will show a more conventional CAPTCHA.

CAPTCHA Catch-22

With all the spam and hacking and bad bots, we often need CAPTCHAs. They block software that creates spam comments, fake registrations or hacks online services. But they also detract from the user experience. And for users with a visual or other disability, they are disastrous.

Google’s latest version of its reCAPTCHA software runs in the background. It does not interrupt users or display challenges, unless it decides the user is high risk.

This solves the user experience issue, although there are still problems with accessibility. But, of course, there is the question of whether we can trust Google with all that data. Seems like there is no simple answer to the problem of being human.

Inside-out Turing?

CAPTCHAs are also used as benchmark tasks for AI technologies. This makes sense. If AI software can pick out all the images of taxis, it will be able to recognise complex objects in scenes.

It feels almost circular. If we use a computer test designed to test that we are human to test how human a computer is, what kind of Turing test is that?

A Stanford study asked people to solve more than 318,000 CAPTCHAs from various schemes. The conclusion was that CAPTCHAs are often harder than they should be. Users fail to correctly solve them 7% – 25% of the time. So I’m not the only person who might actually be a machine.

What do you think about CAPTCHAs? Am I the only maybe-human out there? I’d love to hear your thoughts.

Leave a Comment

Your email address will not be published. Required fields are marked *

Thank You

We're Excited!

Thank you for completing the form. We're excited that you have chosen to contact us about training. We will process the information as soon as we can, and we will do our best to contact you within 1 working day. (Please note that our offices are closed over weekends and public holidays.)

Don't Worry

Our privacy policy ensures your data is safe: Incus Data does not sell or otherwise distribute email addresses. We will not divulge your personal information to anyone unless specifically authorised by you.

If you need any further information, please contact us on tel: (27) 12-666-2020 or email

How can we help you?

Let us contact you about your training requirements. Just fill in a few details, and we’ll get right back to you.