Research map / Large language models / Retrieval and knowledge
From Style to Facts: Mapping the Boundaries of Knowledge Injection with Finetuning
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Large grid-search study (~4,000 LoRA finetuning runs on Gemini v1.5 Pro/Flash) showing knowledge injection via finetuning depends on data format, information type, quantity and evaluation alignment rather than a fundamental gap with task customization.
Problem
Finetuning is commonly believed to work well for style/tone customization but poorly for knowledge injection; it is unclear which factors (not the task-vs-knowledge dichotomy itself) drive this gap.
Approach
Treats task customization and knowledge injection as points on a spectrum and systematically varies information quantity, information type (numerical/categorical/emotional), entity type (real/fictional/persona), training data format, and evaluation task, with controls for confounders.
Key results
- Question-answer training data gives much stronger knowledge generalization than Wikipedia-article training data; Wikipedia-article training yields low accuracy across evaluation tasks.
- Tone teaching reached 96.3% evaluator accuracy (exact match 94.7%), while Wikipedia 2024-event knowledge injection reached only 11% QA accuracy.
- Accuracy falls roughly with a power law as information quantity grows from 20 to 4,000 facts; numerical facts are consistently harder to finetune than categorical or emotional facts.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Teach a target writing tone instead of new Wikipedia facts | Gemini v1.5 Pro LoRA finetuning · Tone teaching vs. Wikipedia fact questions | accuracy: 96.3% vs. 11% | Mixed |
| Use question-answer pairs instead of Wikipedia-style articles for training (ablation) | Gemini v1.5 Pro and Gemini v1.5 Flash · Knowledge-injection evaluation tasks | accuracy | Helped |
| Use reasoning examples instead of question-answer examples for training (ablation) | Gemini v1.5 Pro · Reasoning evaluation tasks | accuracy | Helped |
| Use reasoning examples instead of question-answer examples for training (ablation) | Gemini v1.5 Pro · Direct question-answer evaluation tasks | accuracy | Hurt |
| Train on numerical rather than categorical facts (ablation) | Gemini v1.5 Pro · 20-fact knowledge injection | accuracy | Hurt |
| Train on emotional rather than categorical facts (ablation) | Gemini v1.5 Pro · 20-fact knowledge injection | accuracy | No clear effect |
| Increase the number of facts to learn (ablation) | Gemini v1.5 Pro · Knowledge-injection evaluation tasks | accuracy | Hurt |
| Teach facts about a persona rather than real-world or fictional entities (ablation) | Gemini v1.5 models · 20-fact knowledge injection | accuracy | No clear effect |
| Align the training data format with the evaluation task (ablation) | Gemini v1.5 Pro and Gemini v1.5 Flash · Knowledge-injection evaluation tasks | accuracy | Helped |
| Use question-answer training data instead of Wikipedia articles (ablation) | Gemini v1.5 Pro · Wikipedia fill-in-the-blank evaluation | accuracy | Helped |
| Use question-answer training data instead of Wikipedia articles (ablation) | Gemini v1.5 Pro · Direct question-answer evaluation | accuracy | Helped |
| Apply finetuned knowledge in multi-step reasoning rather than direct recall | Gemini v1.5 models · Reasoning evaluation tasks | accuracy | Hurt |
Surprising findings
- Wikipedia-style articles are among the least effective training formats despite being the most common pretraining format, even after controlling for information density.
- Persona vs. real-world/fictional entity type made no significant difference to finetuning effectiveness once other factors were controlled.
Limitations
- Experiments use proprietary Gemini v1.5 models only, so generality to other model families is untested.
- Mechanisms behind the numerical-vs-categorical gap and Wikipedia-format weakness are not identified.
- Finetuning regime is limited to ~10k-100k token datasets, not continued pretraining.
Experimental setup
Datasets: Wikipedia stub articles (real entities) synthetic fictional entities synthetic personas 2024 Wikipedia articles (meteorology and sports) tone conversations generated from seed chats
Benchmarks: Direct QA Conversational QA Role-play QA Reasoning tasks Wikipedia fill-in-the-blank Wikipedia sentence completion tone matching 2024 Wikipedia exam questions
Metrics: accuracy exact match accuracy
Baselines: in-context learning Wikipedia-article training format
Builds on: LoRA reversal curse random access limitations of autoregressive LMs
Closest papers by meaning
- Understanding Finetuning for Factual Knowledge Extraction (ICML 2024 · similarity 0.89)
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- Delving into the Reversal Curse: How Far Can Large Language Models Generalize? (NeurIPS 2024 · similarity 0.88)
- How new data permeates LLM knowledge and how to dilute it (ICLR 2025 · similarity 0.88)
- TAIA: Large Language Models are Out-of-Distribution Data Learners (NeurIPS 2024 · similarity 0.87)
- From Artificial Needles to Real Haystacks: Improving Retrieval Capabilities in LLMs by Finetuning on Synthetic Data (ICLR 2025 · similarity 0.87)
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