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Fine-Tuning Language Models to Know What They Know
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Proposes a bias-controlled d'_type2 measurement of LLM metacognition and ESMA, an evolution-strategy fine-tuning method with a joint correctness/meta-answer reward that substantially raises d'_type2 for Qwen2.5, Llama3.2 and Gemma3 models.
Problem
Measuring genuine metacognition (self-knowledge) in LLMs is confounded by response biases, heuristics, prompt-template effects and familiarity cues, so raw alignment scores can overstate metacognitive ability.
Approach
Use signal-detection d'_type2 under a dual-question protocol (independent direct and meta prompts) to isolate metacognitive sensitivity, and optimize the model with a gradient-free evolution strategy whose fitness is a joint reward over direct correctness and meta-answer alignment, which is hard to express as per-example backpropagation.
Key results
- ESMA raised d'_type2 for Qwen2.5 1.5B from 0.20 to 0.93 and for Qwen2.5 3B to 1.02, the highest reported value, versus 0.94 for GPT 5.2 and 0.95 for Claude Sonnet 4.5.
- On FictionalQA, ESMA increased d'_type2 for Qwen2.5 1.5B from 0.20 to 0.65 after SFT on fictional QA pairs.
- In the 1.5B ablation, ESMA (d'=0.93) outperformed SFT (0.40), PPO (0.31) and GRPO (0.70) in d'_type2; applying the top 10% of weight updates recovered roughly 80% of the gain.
Surprising findings
- Proprietary models with high accuracy and high raw alignment had lower d'_type2 than the fine-tuned 3B model, e.g. Gemini 3 Flash had d'_type2 0.68 despite 90.71% raw alignment.
- Applying only the top 10% of weight changes by magnitude recovered most of the metacognitive gain, with the remaining 50% of smallest updates contributing almost nothing.
Limitations
- Evaluation limited to factual short-answer retrieval (TriviaQA, FictionalQA); unclear transfer to complex reasoning.
- Performance remains well below human metacognitive standards, per the authors.
- Meta-question-based RL baseline (GRPO) required lower learning rate to avoid reward hacking in univariate settings; reward-hacking risk noted for alignment-only objectives.
Experimental setup
Datasets: TriviaQA FictionalQA
Benchmarks: TriviaQA FictionalQA
Metrics: d'_type2 raw alignment accuracy yes ratio YFR NFR Type 2 AUROC IDK alignment all alignment
Baselines: SFT PPO GRPO OpenAI GPT 5.2 Claude Sonnet 4.5 Gemini 3 Flash
Builds on: Evolution Strategies signal detection theory (meta-d') GRPO PPO
Closest papers by meaning
- Decoupling Metacognition from Cognition: A Framework for Quantifying Metacognitive Ability in LLMs (AAAI 2025 · similarity 0.87)
- metabench - A Sparse Benchmark of Reasoning and Knowledge in Large Language Models (ICLR 2025 · similarity 0.87)
- Tuning-Free Accountable Intervention for LLM Deployment – a Metacognitive Approach (AAAI 2025 · similarity 0.87)
- Dynamic Evaluation of Large Language Models by Meta Probing Agents (ICML 2024 · similarity 0.87)
- Can Large Language Models Derive High-Level Cognition from Low-Level and Fragmented Foundational Information? (AAAI 2025 · similarity 0.87)
- An Emulator for Fine-tuning Large Language Models using Small Language Models (ICLR 2024 · similarity 0.86)
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