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CharacterBench: Benchmarking Character Customization of Large Language Models
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Introduces CharacterBench, a large bilingual generative benchmark (22,859 human-annotated samples, 3,956 characters, 11 dimensions in 6 aspects) for LLM character customization, plus the CharacterJudge evaluator fine-tuned from Qwen2-7B-Chat.
Problem
Existing character-customization benchmarks cover few character categories and dimensions, and feature sparsity in open-ended responses makes generative evaluation ineffective and inefficient.
Approach
Classify evaluation dimensions as sparse or dense by whether character features reliably appear in each response; craft target-oriented queries (from profile/context fragments) for sparse dimensions and target-free queries for dense ones, then train a judge (CharacterJudge) on human scores to score responses cheaply and stably.
Key results
- CharacterJudge reaches substantially higher Pearson correlation with human scores than GPT-4 and GLM-4 judges, with 42% and 36% average improvements over the suboptimal GLM-4-TG on AVG.
- Benchmark ranking of LLMs correlates with human rankings at Spearman 73.1% overall, versus 21.4% for CharacterEval and 38.1% for SocialBench.
- DPO on CharacterGLM-6B with CharacterJudge-scored pairs wins 42.2% vs 34.3% lose against the vanilla model (+7.9 improvement).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use CharacterJudge instead of the strongest automatic-judge baseline | CharacterJudge evaluation on CharacterBench · CharacterBench test, zh/en | Pearson correlation (%): 48/47 -> 68/64 | Helped |
| Add self-consistency (ablation) | CharacterJudge · CharacterBench test, zh/en | Pearson correlation (%): 64/60 -> 68/64 | Helped |
| Add target-based prompting (ablation) | CharacterJudge · CharacterBench test, zh/en | Pearson correlation (%): 51/48 -> 68/64 | Helped |
| Add both self-consistency and target-based prompting (ablation) | CharacterJudge · CharacterBench test, zh/en | Pearson correlation (%): 47/45 -> 68/64 | Helped |
| Fine-tune on highest-scoring benchmark training samples | CharacterGLM-6B · Character customization, human pairwise evaluation | Improve. (%): -0.3 | Hurt |
| Apply DPO using CharacterJudge-scored good-bad response pairs | CharacterGLM-6B-SFT · Character customization, human pairwise evaluation | Improve. (%): 7.9 | Helped |
| Apply DPO rather than SFT alone | CharacterGLM-6B · Character customization, human pairwise evaluation | Improve. (%): 8.5 | Helped |
Surprising findings
- Bilingual fine-tuning was found less effective than training each language separately, so separate Chinese and English judges were trained.
- Most LLMs consistently struggle on the fact accuracy dimension, while morality scores are high across all models.
Limitations
- Morality data contains sensitive and unethical content, requiring restricted access.
- Human-annotation-based scores are limited to a 4-point or other coarse scales per dimension.
Experimental setup
Datasets: CharacterEval test set human role-playing corpus human-prototype interaction corpus synthesized dialogues via prototype interaction
Benchmarks: CharacterBench
Metrics: Pearson correlation with human scores Spearman correlation Kendall correlation win/tie/lose rate average dimension score
Baselines: GPT-4 GPT-3.5-turbo GPT-4-1106 GLM-4 GPT-4o CharacterEval SocialBench CharacterGLM-6B
Builds on: CharacterEval SocialBench direct preference optimization self-consistency
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