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Verifiable reward

As explained in Reinforcement Learning from Human Feedback

A verifiable reward is a reward signal whose correctness can be checked objectively by a procedure or criterion.

A verifiable reward is an objective training signal whose correctness is determined by a scoring procedure rather than a learned judgment. In reinforcement learning from verifiable rewards (RLVR), the procedure can assign a positive reward to a correct completion and 0 to an incorrect one, making a reward model optional. section 7.1

Verifiable rewards fit tasks with definitive outcomes, such as mathematics, coding, or theorem proving. They contrast with preference-based rewards: judging an explanation of opportunity cost requires assessments of clarity, completeness, and helpfulness, while checking a final mathematical answer can be deterministic. section 7.1 section 7.3.1

A practical verification pipeline typically needs:

  • A task with a checkable target, such as a correct answer, executable program behavior, or proved statement. section 7.3.1
  • An answer-extraction convention that isolates the result to be checked. section 7.1
  • A verifier or scoring function that maps the extracted result to reward, often binary correctness. section 7.1

Checking a mathematical completion

For the sum of primes below 20, a completion may place 77 in a boxed final-answer field. A simple extraction rule reads that field; if the extracted answer equals 77, the verifier returns reward 1. The verifier evaluates the answer outcome, not whether every written reasoning step is stylistically preferred. section 7.1

RLVR uses policy-gradient training much like RLHF, but replaces a learned reward model with a verifier where possible. This reduces dependence on proxy preference signals for checkable tasks, while limiting direct applicability to domains where correctness can actually be scored objectively. section 6.6 section 7.1

Modern reasoning training applies this setup at scale on pretrained models. Earlier approaches used ground-truth signals, binary math rewards, code execution, and theorem verification; accessible tooling now includes TRL, Open Instruct, veRL, and OpenRLHF. section 7.2.1 section 7.3.1

How Reinforcement Learning from Human Feedback covers it

How deep it goes
Defines verifier-scored rewards and illustrates extraction plus binary scoring, while deferring detailed optimizer implementation.
Examples
Uses a prime-number summation checked by extracted answer, alongside coding, mathematics, and theorem-proving feedback signals.
What it assumes
Assumes familiarity with reinforcement learning and contrasts learned preference scoring with objective verification.
What you can do after
Apply it via a verifier that extracts a completion outcome and assigns correctness-based reward.
How it connects
Connects RLVR with RLHF, reward models, policy gradients, PPO, chain-of-thought reasoning, and theorem proving.

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This explainer was generated by Manning's knowledge graph from the text of Reinforcement Learning from Human Feedback. The section links point to the parts of the book it draws on.