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SLED: Self Logits Evolution Decoding for Improving Factuality in Large Language Models
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Proposes SLED, a training-free decoding method that contrasts final-layer logits with early-layer logits to estimate a latent factual distribution and applies a single approximate gradient step to refine the output logits, improving factuality on TruthfulQA and FACTOR.
Problem
LLMs often produce factually incorrect outputs even when they latently encode the correct facts; the goal is to use this latent knowledge at inference time to improve factuality without external knowledge bases or fine-tuning.
Approach
Treats the difference between early-layer and final-layer logits as an approximate gradient direction of a KL divergence to the real-world distribution, estimates a latent target distribution by cosine-aligning this direction with one-hot gradients across all early layers (soft, weighted ensemble), and performs one gradient-descent step on the final logits restricted to the top-k tokens.
Key results
- On Gemma-3-1B-PT, SLED raises FACTOR accuracy from 47.83 (greedy) and 12.63 (DoLa) to 63.29.
- On Gemma-3-27B-IT, SLED reaches 73.75 FACTOR and 47.47 TruthfulQA MC1 versus 66.00 and 41.14 for greedy decoding.
- On Mixtral-8x7B, SLED improves FACTOR from 71.41 to 74.92 and MC2 from 49.98 to 57.26 over greedy decoding.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Apply SLED decoding instead of vanilla decoding | Gemma-3 models · FACTOR (Wiki) | FACTOR: 47.83 -> 63.29; 37.17 -> 55.04; 58.78 -> 69.94; 50.17 -> 66.15; 66.67 -> 74.25; 59.12 -> 70.81; 72.04 -> 78.12; 66.00 -> | Helped |
| Apply SLED decoding instead of vanilla decoding | Gemma-2B and Gemma-7B · FACTOR (Wiki) | FACTOR: 50.87 -> 57.05; 60.42 -> 65.56 | Helped |
| Apply SLED decoding instead of vanilla decoding | Mixtral-8×7B and Mixtral-8×7B-IT · FACTOR (Wiki) | FACTOR: 71.41 -> 74.92; 70.51 -> 75.55 | Helped |
| Apply SLED decoding instead of DoLa | gpt-oss-20b · FACTOR (Wiki) | FACTOR: 43.59 -> 55.31 | Helped |
| Apply SLED decoding instead of DoLa | Qwen-3-14B-Base · FACTOR (Wiki) | FACTOR: 58.42 -> 64.09 | Helped |
Surprising findings
- DoLa often underperforms vanilla greedy decoding on FACTOR for Gemma-3 models, dropping FACTOR accuracy by large margins (e.g., 47.83 to 12.63 on Gemma-3-1B-PT).
- A larger DoLa candidate layer set (0-32) performs worse than 0-16, which the authors take as evidence of fragility in layer selection.
Limitations
- Relies on the assumption that early-layer logit differences approximate gradient directions, supported only by empirical cosine-similarity analysis.
- Hyperparameters (evolution rate, scale k) are tuned on a ~5% validation sample of each benchmark.
- Evaluated only on multiple-choice factuality benchmarks; open-ended generation and CoT claims are not clearly backed by reported results in the provided text.
Experimental setup
Datasets: TruthfulQA FACTOR (Wiki)
Benchmarks: TruthfulQA FACTOR (Wiki)
Metrics: MC1 MC2 MC3 FACTOR accuracy
Baselines: DoLa greedy decoding
Builds on: DoLa contrastive decoding
Closest papers by meaning
- Sample Smart, Not Hard: Correctness-First Decoding for Better Reasoning in LLMs (ICLR 2026 · similarity 0.89)
- DoLa: Decoding by Contrasting Layers Improves Factuality in Large Language Models (ICLR 2024 · similarity 0.89)
- SelfJudge: Faster Speculative Decoding via Self-Supervised Judge Verification (ICML 2026 · similarity 0.88)
- Small Language Model Can Self-Correct (AAAI 2024 · similarity 0.88)
- Latent Self-Consistency for Reliable Majority-Set Selection in Short- and Long-Answer Reasoning (AAAI 2026 · similarity 0.87)
- Scalable Best-of-N Selection for Large Language Models via Self-Certainty (NeurIPS 2025 · similarity 0.87)
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