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ELICIT: LLM Augmentation Via External In-context Capability
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Proposes ELICIT, which stores in-context task vectors per task and model in an external capability library, retrieves them with a trained SimCSE-based classifier, and adds them to hidden states at a pre-selected layer to elicit capabilities without extra inference tokens.
Problem
Adapting LLMs to new tasks efficiently: fine-tuning is costly and in-context learning needs demonstrations and extra tokens per inference.
Approach
Build an external library of task vectors (hidden states from 16-shot ICL prompts) with per-task optimal intervention layers, retrieve the relevant vector for a query using a trained binary retriever with threshold filtering, and add it to the hidden state at inference so that zero-shot queries behave like ICL without extra tokens.
Key results
- Across 20 tasks and 4 models, ELICIT averages 11.4% improvement over zero-shot with the same token usage (Llama3 avg 31.2 to 43.5).
- With a math-only library on Mistral, Math accuracy rises from 2.6% to 21.3% while other domains stay roughly unchanged.
- Combining ELICIT with BM25 raises Pythia average from 22.1% to 28.3%.
- The trained retriever reaches AUC 0.96 versus at most 0.28 for cosine, Euclidean, or t-SNE similarity baselines on Llama3.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Apply ELICIT capability vectors | Llama3-8B · 20-task benchmark | average accuracy: 31.2 ± 0.7 -> 43.5 ± 0.8 | Helped |
| Apply ELICIT capability vectors | Mistral-7B · 20-task benchmark | average accuracy: 28.2 ± 0.5 -> 43.7 ± 0.6 | Helped |
| Use a math-only capability library | Mistral-7B · Math domain | accuracy: 2.6% to 21.3% | Helped |
| Use a math-only capability library | Mistral-7B · Reasoning domain | accuracy: 22.3% to 22.4% | Helped |
| Add ELICIT to BM25 retrieval | Pythia-2.8B · In-domain tasks | average accuracy: 22.1 ± 0.5 -> 28.3 ± 0.3 | Helped |
| Add ELICIT to BM25 retrieval | Llama3-8B · In-domain tasks | average accuracy: 55.8 ± 0.7 -> 53.1 ± 1.1 | Hurt |
| Add ELICIT to BM25 retrieval | Mistral-7B · In-domain tasks | average accuracy: 55.5 ± 0.4 -> 53.5 ± 0.5 | Hurt |
| Apply ELICIT to unseen tasks | Llama3-8B · Unseen tasks | average accuracy: 39.9 ± 0.8 -> 45.6 ± 0.4 | Helped |
| Use trained retriever instead of cosine, t-SNE, or Euclidean similarity (ablation) | ELICIT retriever · Llama3-8B retrieval | AUC: 0.28 -> 0.96 | Helped |
| Use top 5 vectors instead of top 10 with DTT (ablation) | ELICIT · Llama3-8B validation set | TP: 45.29 -> 44.71 | Hurt |
| Use top 15 vectors instead of top 10 with DTT (ablation) | ELICIT · Llama3-8B validation set | TP: 45.29 -> 45.02 | Hurt |
| Remove Dynamic Top-K Thresholding (ablation) | ELICIT with n=10 · Llama3-8B validation set | TP: 45.29 -> 45.17 | Hurt |
Surprising findings
- Combining ELICIT with BM25 degrades performance for larger models (Llama3 and Mistral average drops, e.g., Llama3 55.8 to 53.1), while it helps smaller models.
- Higher intervention strength improves task accuracy but degrades language modeling cross-entropy, showing a trade-off.
Limitations
- Zero-shot accuracy of base models with the task template is near zero in the pure ICL setting, so the evaluation relies on added task templates.
- Gains are mixed for larger models when combined with BM25 retrieval.
- Requires building a per-model library and a per-model optimal layer, plus a trained retriever.
Experimental setup
Datasets: CommonsenseQA OpenBookQA HellaSwag BoolQ Big-Bench Hard ARC-Challenge MathQA MMLU Pro-MATH Crows-Pairs BBQ-Age Ethics-Commonsense Ethics-Justice
Benchmarks: CommonsenseQA OpenBookQA HellaSwag BoolQ Big-Bench Hard ARC-Challenge MathQA MMLU Pro-MATH Crows-Pairs BBQ-Age Ethics-Commonsense Ethics-Justice
Metrics: accuracy precision-recall AUC cross-entropy loss on WikiText
Baselines: Zero-shot 16-shot ICL BM25 retrieval (16-shot)
Builds on: task vectors in-context learning BM25 SimCSE
Closest papers by meaning
- LLM Augmented LLMs: Expanding Capabilities through Composition (ICLR 2024 · similarity 0.89)
- Supervised Knowledge Makes Large Language Models Better In-context Learners (ICLR 2024 · similarity 0.89)
- Loquetier: A Virtualized Multi-LoRA Framework for Unified LLM Fine-tuning and Serving (NeurIPS 2025 · similarity 0.88)
- Generative Adapter: Contextualizing Language Models in Parameters with A Single Forward Pass (ICLR 2025 · similarity 0.88)
- EvaLearn: Quantifying the Learning Capability and Efficiency of LLMs via Sequential Problem Solving (NeurIPS 2025 · similarity 0.88)
- Reference Trustable Decoding: A Training-Free Augmentation Paradigm for Large Language Models (NeurIPS 2024 · similarity 0.88)
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