RLHF Explained: How an AI Model Learns What People Prefer

Business Pill 22 · How a model learns what people prefer

A language model that has only read text can continue a sentence, but that is not the same as being helpful. RLHF is the step that taught it what people consider a good answer.

A short explainer video. The numbers in it are round numbers for illustration.

The Short Answer

A language model starts by reading enormous amounts of text. That teaches it to continue any sentence. But continuing a sentence is not the same as being helpful. Ask the raw model a question and it may ramble, dodge, or answer with another question.

How a Judge Is Trained

So people step in. The model writes several answers to the same question. Human reviewers compare them and say which one is better, thousands of times, on thousands of questions.

Those comparisons are used to train a second model, a judge. Its only job is to predict which answer a person would prefer. Now the judgment of thousands of reviewers can be applied millions of times, automatically.

The Loop

Then the loop begins. The model answers, the judge scores it, and the model is adjusted to make high-scoring answers more likely. It tries again, round after round, and drifts toward what people prefer.

This is reinforcement learning from human feedback, RLHF for short. It is the step that turned a text predictor into an assistant you can talk to.

Why It Matters

It matters for business for two reasons. First, the reviewers define what good means: their taste becomes the model’s taste.

Second, the model learns to please. It is rewarded for answers people like, which are not always the answers that are correct. That is why a model can sound confident and agreeable and still be wrong. It was trained on preference, not on truth.

Three Questions to Ask

  1. Who gave the feedback?
  2. What were they asked to prefer?
  3. Is that what your business needs?

How This Concept Connects

Layer 2 of 8 · Models & Training, on the Business Engineer Concept Map

  • RLHF builds on Pretraining. RLHF starts from a model that learned to continue sentences by reading enormous text, then trains it toward helpful answers.
  • RLHF builds on Data Labeling. RLHF depends on human reviewers judging answers, the people-supply-the-answers work of data labeling; their taste becomes the model’s.
  • Guardrails contrasts with RLHF. RLHF shapes behaviour inside the model; a guardrail is a rule enforced by software around the model, checking that it behaved.
  • Preference Gap (lesson unlocks soon) contrasts with RLHF. RLHF teaches a model what reviewers in general prefer; the preference gap is about one person’s taste, closed only by knowing them.
Business Engineer framework
The Four Intelligence Moats
Human preference data as a moat input.
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