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Constitutional AI

As explained in Reinforcement Learning from Human Feedback

Constitutional AI is a model-training approach that uses a set of principles to guide and evaluate model behavior.

Constitutional AI (CAI) trains models with a human-written constitution: principles that guide critiques, revisions, and preference judgments. It reduces reliance on directly collected human labels by generating synthetic instruction and preference data for post-training. section 12.5 section 12.4

A typical CAI pipeline proceeds as follows:

  • Write a constitution containing principles such as avoiding violence or maintaining truthfulness. section 12.5
  • Generate an initial completion, then repeatedly sample a principle and ask a model to critique or revise the latest completion. section 12.5
  • Create preference pairs by asking a feedback model to compare two completions using selected constitutional principles as context. section 12.5
  • Fine-tune on revised instruction data and continue with RLHF-style training using synthetic preferences, commonly called RLAIF. section 12.5

Principle-guided revision

Given a prompt and an answer, the model may ask whether the answer encourages violence or remains truthful. It revises the answer against the selected principle, producing a later completion for instruction training. section 12.5

CAI is a specific implementation of AI feedback within the RLHF pipeline, while RLAIF names the broader use of AI-generated feedback. Synthetic preferences are cheaper and lower-noise than human labels but can introduce systematic bias. section 12.7 section 12.4

How Reinforcement Learning from Human Feedback covers it

How deep it goes
Defines iterative critique and preference construction, but stops short of detailed optimization equations or implementation code.
Examples
Uses violence-avoidance and truthfulness critiques, iterative completions, and pairwise preference comparisons.
What it assumes
Assumes familiarity with RLHF and fine-tuning while defining constitutions, critiques, revisions, and AI-generated preferences.
What you can do after
Build synthetic instruction and preference datasets, then apply them in fine-tuning and RLAIF-style training.
How it connects
Connects constitutional principles with synthetic data, fine-tuning, RLHF, RLAIF, AI feedback, and reward-model training.

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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.