eli5: How do Captcha’s know the correct answer to things and beyond verification what are their purpose?

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I have heard that they are used to train AI and self driving cars and what not, but if thats the case how do they know the right answers to things. IF they need to train AI to know what a traffic light is, how do they know im actually selecting traffic lights? and could we just collectively agree to only select the top right square over and over and would their systems eventually start to believe it that this was the right answer? Sorry this is a lot of questions

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16 Answers

Anonymous 0 Comments

Most of the data in CAPTCHAS have already been verified by humans in control runs. So that grid will have a reference in a database that essentially says “Correct Panels: 1, 3, 5”

What you do as a human that helps AI train, is you contribute your results as error metrics. “Even humans get this wrong.” is a great help to AI, since it can then be taken in as a somewhat acceptable parameter. Let’s say the answers are 1, 3, 5, and 7, but 95+% of humans only mark 1, 3, and 5.

That now becomes a passing result for an AI as well, and they’ll try to get 7 as well, but remember, humans also fail that particular piece, so if the AI misses it, it’s not considered to be part of the error.

Anonymous 0 Comments

Top answer is correct, but ommits some critical information. After all, some Captchas ask you to simply check a box. Asking you to identify the correct images is only half the puzzle.

In the background, it also checks HOW you select the pictures. Computers being robotic, and humans being.. well… humans, we both have very different ways of clicking on things.

A very good example is the timing. Computers generally measure time in milliseconds. There are 1000 milliseconds in a second. If I ask you to click on five objects, the amount of milliseconds between each click would vary, greatly. 500…295…106…952…431.. all (mostly) half a second apart.

Computers have very structured processes. They almost always complete the same action in almost the exact same time (specific to the actual computer, how fast it can generally do things, and how much else its trying to do at the same time). If I was to ask a computer to click on five objects, the milliseconds between would look more like 50… 80… 30… 70…100. They still vary.. but nowhere near as much as a human.

Yes, in this case you could tell the computer to wait a random time between each click, but there are many other details about the way they click that outs them as computers.

We don’t know the full scope of this. If we did, it would he that much easier to make a bot that could fool the system, so companies will not tell you the exacts.

TLDR; They look at the finer details of your mouse clicks (how long it takes between each click as a basic detail, for example), and computer vs human input is very, very different. They still check the right pictures, as others have said, but that’s only half of it. We live in a world of machine learning. Computers can tell which pictures have traffic lights in them pretty easily.

Anonymous 0 Comments

They don’t. They examine your mouse movement and response times to verify you aren’t a robot

Anonymous 0 Comments

Why did they stop being letters? Were algorithms developed that could defeat the letter captcha?

Anonymous 0 Comments

There are a few types of captcha, but I’m going to explain the modern and familiar one from your example, with the traffic lights.

Imagine it’s your job as a human to decide if I am a robot. We are in the same room. You have some pictures, some of which you know are correct, some of which you know are not, and some of which you don’t know.

You show me the pictures and I get the ones that are right, don’t choose the wrong ones and choose some of the unknown ones.

Because I got the right ones right and didn’t choose the wrong ones, I am pre-qualified. You now have to decide if you think I’m human based on when you watched me make the decisions. If I was made of shiny metal and stiff armed and jerky, moving like C-3PO, you know I’m a robot. If I look pretty human but still am stiff you might be suspicious as well. You then either let me go, or give me another chance.

Aside from verification, when someone is takes a captcha, whether they cleared as being human, the choices they made, and how they behaved are all recorded. How they behaved is used to train the program that watches the person to see if they look like C-3PO. The answers to the traffic lights and other objects are collected as a datasets which are used to help further research into computer based learning, as well as for AIs that are used to identify road based features.

Anonymous 0 Comments

Sometimes they don’t know. I had one the other day kept rudly telling me to.click all the buses. I had clicked all the buses. I triple checked. It still wouldn’t let me progress. It definitely thought there was at least one more bus and I was a moron. There wasn’t. I had to click the refresh to get different pictures. I now live in fear that one day I will be declared a robot by a robot with no right of appeal.