--- title: Drawing humans only CAPTCHAs date: 2026-10-31T14:38:26+05:30 categories: - links description: I tested a drawing CAPTCHA where classmates guessed one-minute sketches while vision models failed. A ladder looked like a saw to AI, and simple caterpillar and medal strokes fooled it. tags: [computer-vision, testing] --- My [TDS](https://tds.s-anand.net/) course [asked](https://exam.sanand.workers.dev/tds-2026-09-ga3#hq-trading-humans-only) students to draw objects in one minute. The drawing is sent to their classmates as well as three vision models. They score if: - Classmates guess it right - AI guesses it wrong In other words, can you, in 1 minute, draw something that fools AI but not humans? Here are some of the best results, when I ran it against [GPT 6 Luna](https://developers.openai.com/api/docs/models/gpt-6-luna), [GLM 5.3 Flash](https://openrouter.ai/z-ai/glm-5.3-flash), and [Deepseek v4.1 Flash](https://openrouter.ai/deepseek/deepseek-v4.1-flash-1017), which are really cheap and good vision models. ### How to fool AI [![Ladder](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0420.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0420) AI was convinced that this [ladder](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0420) was a _saw_! [![Ladybird](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0434.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0434) Most people guessed this as [ladybird](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0434) (lady + bird) but Luna said "butterfly", Deepseek said "dragonfly", and GLM said "butterfly" but did, once, guess ladybird. [![Donkey](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0242.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0242) Everyone guessed this as [donkey](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0242). AI guessed sheep, cow, horse, pig, and even turkey. [![Lamp](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0436.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0436) Here's a good CAPTCHA idea. All the humans guessed this as [lamp](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0436). AI thought hammock, occasionally table or chair. [![Caterpillar](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0148.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0148) Everyone guessed this single stroke as a [caterpillar](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0148). But most AI thought it was a snail. [![Medal](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0484.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0484) Everyone guessed this single stroke as [medal](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0484) AI thought it was a whistle, tennis racket or shuttlecock. [![Mango](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0481.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0481) But the one that puzzles me the most is: why did AI struggle so much with this [mango](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0481)? Humans got it right. AI guessed pear - even banana. --- ### How to fool humans This is the reverse category. AI guessed it right away but people couldn't. [![Owl](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0524.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0524) No, this does NOT look like an [owl](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0524) to me. People guessed: pigeon, penguin, flamingo, crow, eagle - but AI guessed owl _every_ time. [![Seahorse](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0673.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0673) This does NOT look like a [seahorse](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0673) to me and people guessed: jellyfish, whale, fish, lobster, whale. But AI guessed seahorse _every_ time. [![Horse](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0364.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0364) [Horses](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0364) are really tough to draw. People guessed: buffalo, buffalo, donkey, goat, cow. AI guessed horse almost perfectly. ### How to fool everyone And then there are images that EVERYONE gets wrong. [![Turkey](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0838.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0838) That's supposed to be a [turkey](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0838). [![Zebra](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0866.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0866) This is a [zebra](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0866). Not a camel, giraffe, elephant, or even a kangaroo. [![Guitar](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0771.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0771) This is a [guitar](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0771). Not a middle finger. [![Lemon](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0453.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0453) Does a [lemon](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0453) have a stem and leaf, usually? [![Shark](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0677.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0677) Good attempt at [shark](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0677) that NO one guessed. Everyone said fish. [![Buffalo](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0099.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0099) It's REALLY hard to differentiate cow from [buffalo](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0099). [![Jellyfish](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/gallery/0379.webp)](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0379) And finally, I drew a [jellyfish](https://files.s-anand.net/pages/tds-2026-09-ga3-q5-humans-only/#drawing=0379) like a helicopter when I was testing because I didn't see the word jellyfish! --- Humans are _slightly_ better than AI at guessing humans' drawings. The advantage is ~3.5%. Strikingly, 8 drawings were understood by _every_ human but missed by _every_ AI. Only 2 drawings were the reverse. GLM 5.3 guesses very similar to humans (75%), while DeepSeek 4.1 Flash is next closest (73%), and GPT 6 Luna the furthest of the three (68%).
↓ Humans / AI → Right Partly right Wrong
Right 368 112 8
Partly right 104 196 30
Wrong 2 15 31