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HOW MODELS LEARN

RLHF.

Reinforcement learning from human feedback

Using human feedback to help train a model toward preferred behavior.

In plain words

Reinforcement learning from human feedback is a family of training methods that use people’s judgments to shape a model’s behavior. It is often used to improve the usefulness of language-model responses.

A closer look

In a common approach, people compare candidate responses. Those comparisons train a reward model that estimates which outputs people would prefer. Reinforcement learning then adjusts the language model to receive higher rewards, often with constraints that limit how far it moves from a reference model.

Human feedback is valuable but imperfect. Preferences may be inconsistent, task-specific, or influenced by persuasive writing. A reward model is only a proxy for the qualities people care about, and optimizing it too strongly can exploit its mistakes. Related preference-training methods can skip parts of this pipeline and are not all reinforcement learning in the strict sense.

In practice

AN EXAMPLE

Reviewers prefer answers that acknowledge uncertainty over equally fluent answers that invent facts. Training uses those preferences to encourage more appropriate responses on similar tasks.

A useful distinction

RLHF does not directly install a complete set of human values or guarantee truthfulness. It optimizes a training signal derived from a particular feedback process and must be evaluated for side effects.

Sources & further reading

Ouyang et al. — Training language models to follow instructions with human feedback (opens in a new tab)