LLMs Exhibit Significantly Lower Uncertainty in Creative Writing Than Professional Writers
Organizations: Department of English, McGill University
Abstract
We argue that uncertainty is a key and understudied limitation of LLMs' performance in creative writing, which is often characterized as trite and cliché-ridden. Literary theory identifies uncertainty as a necessary condition for creative expression, while current alignment strategies steer models away from uncertain outputs to ensure factuality and reduce hallucination. We formalize this tension by quantifying the ``uncertainty gap'' between human-authored stories and model-generated continuations. Through a controlled information-theoretic analysis of 28 LLMs on high-quality storytelling datasets, we demonstrate that human writing consistently exhibits significantly higher uncertainty than model outputs. We find that instruction-tuned and reasoning models exacerbate this trend compared to their base counterparts; furthermore, the gap is more pronounced in creative writing than in functional domains, and shows a consistent correlation with writing quality. Achieving human-level creativity requires new uncertainty-aware alignment paradigms that can distinguish between destructive hallucinations and the constructive ambiguity required for literary richness.
Figures & tables
| Base | Instruct | Thinking | ||||||||||
| Model | NLL | PPL | PMI | CPMI | NLL | PPL | PMI | CPMI | NLL | PPL | PMI | CPMI |
| OLMo-2-7B | 2.18 | 3.62 | -1.70 | 0.13 | 3.01 | 5.97 | -1.89 | 0.01 | ||||
| OLMo-2-13B | 2.19 | 3.48 | -1.63 | 0.12 | 2.48 | 4.14 | -1.77 | 0.10 | ||||
| OLMo-2-32B | 2.15 | 3.19 | -1.55 | 0.08 | 2.32 | 3.51 | -1.64 | 0.07 | ||||
| OLMo-3-7B | 2.20 | 3.95 | -1.81 | 0.15 | 3.30 | 7.98 | -2.20 | 0.09 | 2.74 | 6.07 | -2.17 | 0.11 |
| OLMo-3-32B | 2.15 | 3.47 | -1.66 | 0.09 | 2.99 | 5.59 | -1.68 | -0.43 | 2.78 | 5.06 | -1.66 | -0.40 |
| Domain | NLL | PPL | PMI ( ) | CPMI ( ) |
| Essays | 3.07 | 6.03 | ||
| News (Reuters) | 3.31 | 5.91 | ||
| Creative Writing | 3.11 | 6.60 |
| Source | Metric | Sig. | % Linear | Sweet Spot | % Diminishing | |
| Human | NLL | 56% | 12% | 34% | 9% | |
| PPL | 56% | 5% | 0% | 25% | ||
| PMI | 75% | 44% | 2% | 0% | ||
| Model | NLL | 77% | 28% | 31% | 19% | |
| PPL | 77% | 9% | 31% | 33% | ||
| PMI | 69% | 45% | 2% | 0% |
Appendix figures & tables17 assets
Supplementary material from the paper’s appendix.
Appendix
| UE Metric | Higher Value Indicates | Scope |
| Token Entropy | More uncertainty | Token |
| Perplexity | More uncertainty | Sequence |
| PMI | More predictable by context | Sequence |
| CPMI | Uncertainty at key positions | Sequence |
| New Yorker | Tell-Me-A-Story | |||||||||||
| Family | Variant | PMI | CPMI | PMI | CPMI | Localization | ||||||
| OLMo-2-7B | Base | 1.70 | +0.13 | +1.29 | 1.14 | 0.67 | 1.55 | +0.04 | +1.15 | 1.08 | 0.70 | filler |
| OLMo-2-7B | Instruct | 1.89 | +0.01 | +1.79 | 1.79 | 0.95 | 1.85 | +0.01 | +1.70 | 1.70 | 0.92 | uniform |
| OLMo-2-13B | Base | 1.63 | +0.12 | +1.25 | 1.11 | 0.68 | 1.48 | +0.03 | +1.11 | 1.07 | 0.72 | filler |
| OLMo-2-13B | Instruct | 1.77 | +0.10 | +1.42 | 1.30 | 0.74 | 1.69 | +0.05 | +1.34 | 1.27 | 0.75 | filler |
| OLMo-2-32B | Base | 1.55 | +0.08 | +1.16 | 1.07 | 0.69 | 1.45 | +0.01 | +1.07 | 1.04 | 0.72 | filler |
| New Yorker | Tell-Me-A-Story | |||||||
| Source | NLL | PPL | PMI | CPMI | NLL | PPL | PMI | CPMI |
| Human (ground truth) | 3.11 | 22.53 | 1.31 | 0.24 | 2.78 | 16.08 | 1.52 | 0.21 |
| Qwen3-4B-Instruct | 2.85 | 17.29 | 1.73 | 0.09 | 2.56 | 12.95 | 2.05 | 0.25 |
| OLMo-3-7B-Instruct | 3.06 | 21.28 | 1.77 | 0.08 | 2.71 | 15.03 | 2.12 | 0.24 |
| Gemma-3-4B-it | 2.74 | 15.42 | 1.82 | 0.19 | 2.39 | 10.88 | 2.25 | 0.37 |
| Gemma-3-12B-it | 2.74 | 15.50 | 1.93 | 0.21 | 2.41 | 11.16 | 2.35 | 0.41 |
| Dataset | Total Stories | After Filtering | Sentences | Tokens | Writers | Data Source | Availability | Memorization Risk |
| New Yorker | 504 | 70 | 9,144 | 201,199 | Expert, some prize-winning | The New Yorker magazine | Private | Very Low |
| Tell_Me_a_Story ( Huot et al., 2025 ) | 230 | 226 | 23,218 | 500,452 | Professional | Story workshop | Public (requires decryption) | Low |
| Ghostbuster ( Verma et al., 2024 ) | 299 | 298 | 10,010 | 213,749 | Lay | Reddit (r/WritingPrompts) | Public | Medium |
| Essays | News (Reuters) | Creative Writing | |||||||||||
| Model | Size | NLL | PPL | PMI | CPMI | NLL | PPL | PMI | CPMI | NLL | PPL | PMI | CPMI |
| OLMo-2-Instruct | 7B | 3.45 | 7.14 | 0.24 | 3.46 | 6.16 | 0.20 | 3.46 | 7.43 | 0.01 | |||
| OLMo-2-Instruct | 13B | 2.85 | 5.11 | 0.25 | 2.86 | 4.48 | 0.20 | 2.68 | 4.85 | 0.08 | |||
| OLMo-3-Instruct | 7B | 3.30 | 7.32 | 0.25 | 3.62 | 8.07 | 0.26 | 3.51 | 8.94 | 0.05 | |||
| Llama-3.1-Instruct | 8B | 2.15 | 3.79 | 2.27 | 3.47 | 2.17 | 3.95 | ||||||
| Qwen3-Instruct | 4B | 3.25 | 6.60 | 0.34 | 3.51 | 6.92 | 0.32 | 3.55 | 8.33 | 0.21 | |||
| Model | vs. Essays (%) | vs. News (%) |
| OLMo-2-7B-Instruct | +28.3 | +26.0 |
| OLMo-2-13B-Instruct | +23.4 | +22.6 |
| OLMo-3-7B-Instruct | +21.4 | +3.6 |
| Llama-3.1-8B-Instruct | +35.3 | +52.3 |
| Qwen3-4B-Instruct | +8.7 | +10.9 |
| Phi-4 | +12.3 | +16.0 |
| Target | Comparison | Metric | Sig. in expected dir. | Median |
| Human–model gap | Base Instruct | NLL | 18/22 | 1.00 |
| Human–model gap | Base Instruct | PPL | 20/22 | 1.00 |
| Human–model gap | Base Instruct | PMI | 14/22 | 0.75 |
| Human–model gap | Base Instruct | CPMI | 12/22 | 0.80 |
| Human–model gap | Base Thinking | NLL | 6/6 | 1.00 |
| Human–model gap | Base Thinking | PPL | 6/6 | 1.00 |
| Family | NLL | PPL | PMI | CPMI |
| New Yorker | ||||
| OLMo-2-7B | ∗∗∗ | ∗∗∗ | ∗∗∗ | ∗∗∗ |
| OLMo-2-13B | ∗∗∗ | ∗∗∗ | ∗∗∗ | |
| OLMo-2-32B | ∗∗∗ | ∗∗∗ | ∗∗∗ | |
| OLMo-3-7B | ∗∗∗ | ∗∗∗ | ∗∗∗ | ∗∗∗ |
| OLMo-3-32B | ∗∗∗ | ∗∗∗ | ∗∗∗ | |
| Family | NLL | PPL | PMI | CPMI |
| New Yorker | ||||
| OLMo-3-7B | 2.20 2.76 ∗∗∗ | 4.10 6.19 ∗∗∗ | 1.80 2.18 ∗∗∗ | 0.17 0.15 |
| OLMo-3-32B | 2.16 2.78 ∗∗∗ | 3.52 5.25 ∗∗∗ | 1.69 1.66 | 0.11 0.36 ∗∗∗ |
| Qwen3-4B | 2.22 3.35 ∗∗∗ | 4.16 8.37 ∗∗∗ | 1.74 1.56 ∗∗∗ | 0.20 0.28 ∗∗∗ |
| Tell-Me-A-Story | ||||
| OLMo-3-7B | 2.15 2.76 ∗∗∗ | 3.36 5.15 ∗∗∗ | 1.66 2.03 ∗∗∗ | 0.06 0.05 |
| New Yorker | Tell-Me-A-Story | |||
| Family | NLL | PPL | NLL | PPL |
| OLMo-2-7B | 1.11 0.91 ∗∗∗ | 3.03 2.48 ∗∗∗ | 1.01 0.78 ∗∗∗ | 2.76 2.17 ∗∗∗ |
| OLMo-2-13B | 1.07 0.98 ∗∗∗ | 2.91 2.67 ∗∗∗ | 0.98 0.86 ∗∗∗ | 2.66 2.36 ∗∗∗ |
| OLMo-2-32B | 1.04 0.97 ∗∗∗ | 2.82 2.64 ∗∗∗ | 0.95 0.88 ∗∗∗ | 2.60 2.41 ∗∗∗ |
| OLMo-3-7B | 1.16 0.91 ∗∗∗ | 3.21 2.48 ∗∗∗ | 1.07 0.80 ∗∗∗ | 2.90 2.23 ∗∗∗ |
| OLMo-3-32B | 1.09 0.88 ∗∗∗ | 2.98 2.41 ∗∗∗ | 1.00 0.79 ∗∗∗ | 2.73 2.20 ∗∗∗ |
| Family | Variant | NLL ratio | PPL ratio | PMI gap | CPMI gap |
| New Yorker | |||||
| OLMo-2 | Base | 2.18 2.15 ∗ | 3.67 3.38 ∗∗∗ | 1.71 1.56 ∗∗∗ | +0.15 +0.11 ∗ |
| OLMo-2 | Instruct | 3.02 2.32 ∗∗∗ | 6.26 3.71 ∗∗∗ | 1.87 1.67 ∗∗∗ | +0.03 +0.09 ∗∗∗ |
| OLMo-3 | Base | 2.20 2.16 ∗∗ | 4.10 3.52 ∗∗∗ | 1.80 1.69 ∗∗∗ | +0.17 +0.11 ∗∗∗ |
| OLMo-3 | Instruct | 3.33 3.00 ∗∗∗ | 8.55 5.88 ∗∗∗ | 2.22 1.67 ∗∗∗ | +0.13 0.37 ∗∗∗ |
| OLMo-3 | Thinking | 2.76 2.78 (ns) | 6.19 5.25 ∗∗∗ | 2.18 1.66 ∗∗∗ | +0.15 0.36 ∗∗∗ |
| Family | NLL tax | PPL tax | PMI tax | CPMI tax |
| New Yorker | ||||
| OLMo-2 (7B 32B) | +0.83 +0.16 ∗∗∗ | +2.44 +0.34 ∗∗∗ | 0.19 0.10 ∗∗∗ | 0.11 0.01 ∗∗∗ |
| OLMo-3 (7B 32B) | +1.12 +0.86 ∗∗∗ | +4.22 +2.22 ∗∗∗ | 0.38 0.03 ∗∗∗ | 0.04 0.47 ∗∗∗ |
| Gemma-3 (4B 27B) | +1.72 +1.26 ∗∗∗ | +5.15 +2.92 ∗∗∗ | +0.10 0.15 ∗∗∗ | 0.46 0.06 ∗∗∗ |
| Tell-Me-A-Story | ||||
| OLMo-2 (7B 32B) | +1.08 +0.28 ∗∗∗ | +2.39 +0.49 ∗∗∗ | 0.29 0.10 ∗∗∗ | 0.03 +0.02 ∗∗∗ |
| Setting | OLMo-2-7B | Llama-3.1-8B | Qwen3-4B | Gemma-3-4B |
| Gap in NLL (nats) | ||||
| 1.87 / 1.81 | 1.38 / 1.22 | 2.00 / 1.83 | 2.23 / 1.96 | |
| 1.81 / 1.72 | 1.33 / 1.17 | 2.02 / 1.86 | 2.23 / 1.96 | |
| 1.67 / 1.63 | 0.33 / 0.29 | 1.81 / 1.67 | 2.08 / 1.82 | |
| VS | 0.10 / 0.25 | 0.40 / 0.27 | - | - |
| Gap in PMI (nats) | ||||
| Dataset | Source | Metric | Sig.+ | Sig.– | Sweet | |||||
| ghostbuster | Human | NLL | 8 | 0.122 | 0.021 | 100% | 0% | 0% | – | 0.0008 |
| Human | PMI | 8 | -0.077 | 0.025 | 0% | 88% | 12% | -0.68 | 0.0007 | |
| Human | PPL | 8 | 0.122 | 0.021 | 100% | 0% | 0% | – | 0.0008 | |
| Model | NLL | 8 | 0.176 | 0.033 | 100% | 0% | 0% | – | 0.0016 | |
| Model | PMI | 8 | -0.031 | 0.030 | 0% | 25% | 0% | – | 0.0009 | |
| Model | PPL | 8 | 0.176 | 0.033 | 100% | 0% | 0% | – | 0.0046 |
| New Yorker | TellMeAStory | Ghostbuster | ||||
| Model | Human | Model | Human | Model | Human | Model |
| Qwen3-4B-Base | 0.029 | 0.018 | 0.130 ∗∗∗ | 0.121 ∗∗∗ | – | – |
| Qwen3-4B-Instruct-2507 | 0.015 | 0.100 ∗∗ | 0.095 ∗∗∗ | 0.167 ∗∗∗ | 0.112 ∗∗∗ | 0.176 ∗∗∗ |
| Qwen3-4B-Thinking-2507 | 0.017 | 0.064 ∗ | 0.090 ∗∗∗ | 0.109 ∗∗∗ | – | – |
| OLMo-2-0325-32B | 0.007 | 0.017 | 0.134 ∗∗∗ | 0.153 ∗∗∗ | – | – |
| OLMo-2-0325-32B-Instruct | 0.006 | 0.026 | 0.111 ∗∗∗ | 0.162 ∗∗∗ | – | – |
| Dataset | Source | Metric | Linear | Sweet Spot | Diminishing | ||
| ghostbuster | Human | NLL | 0.055 | -0.0038 | 100% | 0% | 0% |
| Human | PMI | -0.036 | -0.0015 | 75% | 12% | 0% | |
| Human | PPL | 0.059 | -0.0017 | 38% | 0% | 12% | |
| Model | NLL | 0.077 | -0.0014 | 75% | 0% | 12% | |
| Model | PMI | -0.021 | 0.0041 | 12% | 0% | 0% | |
| Model | PPL | 0.092 | -0.0091 | 25% | 0% | 75% |
| Source | Metric | Linear | Sweet Spot | Diminishing | U-Shape | Flat/NS |
| Human | NLL | 8 | 22 | 6 | 0 | 28 |
| PPL | 3 | 0 | 16 | 0 | 45 | |
| PMI | 28 | 1 | 0 | 0 | 35 | |
| Model | NLL | 18 | 20 | 12 | 1 | 13 |
| PPL | 6 | 20 | 21 | 0 | 17 | |
| PMI | 29 | 1 | 0 | 3 | 31 |
Text Generation
Text generation studies methods for producing coherent, useful language from prompts, data, and dialogue context.
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