DEEP EXPLANATION

What Is RLHF and How Does It Shape Model Behavior? (ANSWERED)

Model BasedLLMsMedium15 min read

Model question on RLHF — SFT, reward model, PPO alignment, and how human preferences change helpfulness vs hallucination trade-offs.

TL;DR — Quick Answer

RLHF aligns LLMs with human preferences after pretraining. Typical pipeline: (1) Supervised Fine-Tuning (SFT) on high-quality demonstrations, (2) train a reward model from human comparisons of outputs, (3) optimize the policy with RL (often PPO) to maximize reward while staying close to the base model (KL penalty). RLHF improves helpfulness, instruction-following, and safety tone but does not eliminate hallucinations — it optimizes perceived quality, not factual verification.

The Interview Question

What is Reinforcement Learning from Human Feedback (RLHF)? Explain how it shapes LLM behavior after pretraining.

Deep Explanation

Pretraining vs alignment

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RLHFAlignmentSFTPPOHuman FeedbackOpenAIAnthropicGoogle

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