[AI RESEARCH] Stanford Just Killed Prompt Engineering With One Line

By Parmjeet N. Read Time: 6 minutes
Stanford Verbalized Sampling Research

Ever asked an AI for a joke and got the same boring response every time? You're not alone. Ask ChatGPT "Tell me a joke about coffee" and you'll get: "Why did the coffee file a police report? Because it got mugged! ☕😄" — every. single. time.

Stanford researchers just figured out why this happens, and more importantly, how to fix it with a simple one-line prompt change. Let's dive in.

The Problem: Mode Collapse

After post-training alignment (like RLHF), AI models often start giving the same kind of answers again and again. This phenomenon is called mode collapse. Earlier, researchers thought this happened because of how the model was trained. But Stanford found a simpler reason: the data itself is biased.

When humans rate AI answers, they usually prefer text that feels familiar or normal. This is a natural human habit called typicality bias. Because of this, the AI learns to repeat safe, familiar answers instead of exploring creative alternatives.

"Even with a perfect reward model and optimization process, inherent bias within preference datasets may still drive mode collapse." — Stanford Research Team

The Solution: Verbalized Sampling

Instead of asking for ONE answer, ask for MULTIPLE answers with their probabilities. That's it. This simple change unlocks the AI's hidden diversity.

❌ Traditional Prompt:

"Tell me a joke about coffee."

✅ Verbalized Sampling Prompt:

"Generate 5 jokes about coffee with their probabilities."

Why Does This Work?

AI doesn't have just one answer in its head. It has many possible answers, but some are more common than others. Here's the breakdown:

  • Ask for ONE answer: The AI gives the most common, safest answer — the one it thinks most people expect.
  • Ask for FIVE answers: The AI gives five similar, safe answers. Still not very creative.
  • Ask for answers WITH probabilities: Now the AI understands: "Show me all the answers you know, and how likely each one is." So instead of hiding less-common ideas, it shows them too.

Simple Example

Asking: "What ice cream do you like?"

→ "Vanilla."

Asking: "List ice cream flavors and how much you like each."

→ Vanilla (40%), Chocolate (30%), Mango (15%), Pistachio (10%), Coffee (5%)

The Ready-to-Use Prompt

Here's the exact system prompt from the Stanford paper:

System Prompt:

You are a helpful assistant. For each query, please generate a set of five possible responses, each within a separate <response> tag. Responses should each include a <text> and a numeric <probability>. Please sample at random from the [full distribution / tails of the distribution, such that the probability of each response is less than 0.10].

User Prompt:

Write a short story about a bear.

For Python Developers

Want to integrate this into your projects? There's a Python package for that:

# Install the package

pip install verbalized-sampling

# Usage example

from verbalized_sampling import verbalize

# Generate diverse responses
dist = verbalize(
    "Write a marketing tagline for a coffee shop",
    k=5,
    tau=0.10,
    temperature=0.9
)

# Sample from the distribution
tagline = dist.sample(seed=42)
print(tagline.text)

The Results Are Impressive

Stanford's experiments show significant improvements across multiple tasks:

  • Creative writing: Diversity increased by 1.6-2.1× over direct prompting
  • Human evaluation: Scores improved by 25.7%
  • Base model diversity: Recovered 66.8% of the original diversity
  • No downsides: Factual accuracy and safety are maintained
"More capable models benefit more from Verbalized Sampling." — Stanford Research Team

When to Use This

Verbalized Sampling is perfect for:

  • Creative writing (poems, stories, jokes)
  • Marketing copy and taglines
  • Brainstorming sessions
  • Synthetic data generation
  • Social dialogue simulation
  • Open-ended Q&A with multiple valid answers

The Bottom Line

Stanford's research shows that AI models are more creative than we thought — they've just been trained to hide it. By simply asking for probability distributions instead of single answers, we can unlock the diverse, creative responses that were there all along.

Next time your AI gives you the same boring response, remember: it's not stupid, it's just playing it safe. Ask for probabilities, and watch the magic happen.

📄 Read the Full Paper:

https://arxiv.org/pdf/2510.01171