Experiments exploring how language models handle randomness. We asked Claude to "pick a name at random" 37,500 times across five models and dozens of prompt variations, then analyzed the results.

The full writeup is published here: Marcus, Marcus, Marcus!

Key findings:

• The most common male name was "Marcus", chosen 4,367 times (23.6%)
• Opus 4.5 returned "Marcus" 100 out of 100 times with the simple prompt
• Nine parameter combinations produced zero entropy — perfectly deterministic output
• Elaborate prompts doubled unique names but introduced different biases
• Random word seeds were more effective than random noise at increasing diversity

To run experiments, you'll need an Anthropic API key in a .env file:

ANTHROPIC_API_KEY=your-key-here

Run the experiment (calls the Anthropic API — this costs real money):

npm run experiment:random-names

Run the analysis on collected results:

npm run analysis:random-names

The output/ directory contains:

• random-names.tar.gz — All 37,500 individual JSON responses, archived. Extract with tar xzf output/random-names.tar.gz -C output/ to get the individual files.
• random-names-analysis.json — Full statistical analysis including per-model breakdowns, entropy calculations, and cross-parameter comparisons.
• actual-costs.json — Real API costs from running the experiment ($27.58 total).