Ask an AI for a number between 1 and 10, and you get 7

Ask a chatbot for a random number between 1 and 10, and chances are you'll get 7. I tried it in ChatGPT and in Claude Opus 5.5, each in a fresh conversation, and got the same answer twice, straight away: 7.

That's no coincidence. In a 2025 study, GPT-4o-mini, Phi-4 and Gemini 2.0 picked 7 in about 80% of cases, and 7 was the favourite of all six models tested.

The funny part is that we humans do it too. When YouGov asked Britons for a random number between 1 and 10, a third picked 7, where pure chance would give you 10%. 7 simply feels random: it isn't an extreme, it isn't the middle and it isn't even. The models most likely picked up that habit from us.

So if you need to draw a winner for a contest, don't leave it to a chatbot.