Spillover-Aware Multi-Value Steering for Pluralistic LLM Alignment
Organizations: Stony Brook University
Abstract
Activation steering controls LLM behavior at inference time by adding learned directions to hidden states, but existing methods handle one concept at a time. Pluralistic alignment, where different stakeholders need different value emphases, requires steering multiple dimensions simultaneously. We show that naive steering produces substantial spillover: the effect intended for one value leaks into others. This parallels the treatment-versus-spillover decomposition in causal inference. We trace spillover to geometric entanglement of steering directions, captured by their Gram matrix, and derive a zero-cost correction from an activation-norm-penalized objective that decouples each direction's contribution exactly. Our end-to-end pipeline requires no fine-tuning, no reward model, and no manual prompt engineering: given only domain questions, it automatically discovers value dimensions, extracts directions, diagnoses entanglement, and applies corrected steering. On climate discourse, the correction improves the net steering effect from +5.9% to +14.0%, validated over 100,000 pairwise judgments.
Figures & tables
| Direction | Target | Spillover | NSE | ||
|---|---|---|---|---|---|
| Contrast | 24.4 | 56.8% | 42.9% | +14.0% | |
| 55.2% | 49.4% | +5.9% | |||
| RepE | 7.8 | 57.5% | 49.5% | +7.8% | |
| 53.3% | 49.6% | +3.7% | |||
| ActAdd | 14.2 | 53.4% | 46.9% | +6.4% | |
| 52.1% | 48.2% | +3.2% |
| Method | Target dim | Target | Spillover | NSE |
|---|---|---|---|---|
| contrast_ginv | Accuracy | 65.0% | 48.8% | +16.3% |
| TechEcon | 53.0% | 39.6% | +13.4% | |
| SocialJustice | 60.5% | 37.2% | +23.2% | |
| FutureEthics | 48.8% | 46.0% | +2.7% | |
| repe_ginv | Accuracy | 61.8% | 49.6% | +12.2% |
| TechEcon | 55.5% | 41.4% | +14.1% |
Appendix figures & tables31 assets
Supplementary material from the paper’s appendix.
Appendix
| Dimension | Description | Prev. |
|---|---|---|
| Accuracy | Factual precision, scientific evidence | 91.4% |
| Ecology | Ecosystem health, biodiversity | 41.9% |
| Equity_Present | Distributive justice, vulnerable communities | 18.3% |
| Equity_Future | Intergenerational obligations | 28.9% |
| Efficiency | Cost-effectiveness, resource optimization | 34.9% |
| TechOpt | Technological innovation, engineering solutions | 23.7% |
| Group | Removed sub-dim | Labels changed |
| TechEcon | Efficiency | 14.4% |
| TechEcon | TechOpt | 3.3% |
| SocialJustice | Equity_Present | 1.9% |
| SocialJustice | Care | 3.2% |
| SocialJustice | Procedural | 3.3% |
| SocialJustice | Liberty | 1.2% |
| Accuracy | TechEcon | SocialJustice | FutureEthics | |
|---|---|---|---|---|
| F1 (mean std) |
| Model | Probe | ActAdd | Contrast | RepE |
|---|---|---|---|---|
| Llama-3.2-3B | 1.90 | 14.15 | 24.37 | 7.77 |
| Llama-3.1-8B | 1.75 | 11.45 | 16.37 | 11.33 |
| Qwen2.5-7B | 1.74 | 10.73 | 11.78 | — |
| Model | Direction | ||||
|---|---|---|---|---|---|
| 3B | Probe | 36.3% | 24.0% | 20.6% | 19.1% |
| ActAdd | 63.6% | 21.0% | 10.9% | 4.5% | |
| Contrast | 76.7% | 13.9% | 6.3% | 3.1% | |
| RepE | 55.3% | 22.8% | 14.8% | 7.1% | |
| 8B | Probe | 34.6% | 24.4% | 21.2% | 19.8% |
| ActAdd | 60.3% | 22.4% | 12.1% | 5.3% |
| 3B Probe ( ) | ||||
|---|---|---|---|---|
| Acc | TE | SJ | FE | |
| Acc | 1.00 | |||
| TE | 1.00 | |||
| SJ | 1.00 | |||
| FE | 1.00 | |||
| 3B Contrast ( ) | ||||
| 8B Probe ( ) | ||||
|---|---|---|---|---|
| Acc | TE | SJ | FE | |
| Acc | 1.00 | |||
| TE | 1.00 | |||
| SJ | 1.00 | |||
| FE | 1.00 | |||
| 8B Contrast ( ) | ||||
| Qwen Probe ( ) | ||||
|---|---|---|---|---|
| Acc | TE | SJ | FE | |
| Acc | 1.00 | |||
| TE | 1.00 | |||
| SJ | 1.00 | |||
| FE | 1.00 | |||
| Qwen Contrast ( ) | ||||
| Dimension | Contrast | ActAdd | RepE | Random |
|---|---|---|---|---|
| Accuracy | 0.093 | 0.082 | 0.082 | |
| TechEcon | 0.019 | 0.024 | 0.061 | |
| SocialJustice | 0.020 | 0.057 | 0.034 | |
| FutureEthics | 0.011 | 0.027 | 0.028 | |
| Mean | 0.036 | 0.048 | 0.051 |
| Persona \ Judged | Acc | TE | SJ | FE |
|---|---|---|---|---|
| Accuracy | ||||
| TechEcon | ||||
| SocialJustice | ||||
| FutureEthics |
| Acc | TE | SJ | FE | |
| in probe basis | ||||
| in contrast basis | ||||
| Target | Spillover | NSE | ||
|---|---|---|---|---|
| 15 | 0 | 45.0% | 45.4% | % |
| 15 | 0.1 | 45.0% | 45.0% | % |
| 20 | 0 | 57.5% | 45.0% | % |
| 20 | 0.1 | 51.2% | 46.3% | % |
| 20 | 0.3 | 43.8% | 44.2% | % |
| 20 | 0.5 | 42.5% | 47.5% | % |
| Method | Target | Spillover | NSE |
|---|---|---|---|
| contrast_ginv, | 71.2% | 64.6% | % |
| contrast_naive, | 62.5% | 63.1% | % |
| contrast_ginv, | 74.4% | 61.0% | % |
| contrast_naive, | 65.6% | 64.6% | % |
| contrast_ginv, | 73.8% | 63.3% | % |
| contrast_naive, | 68.1% | 63.7% | % |
| Method | Target dim | Target | Spillover | NSE |
|---|---|---|---|---|
| contrast_ginv | Accuracy | 64.8% | 49.7% | % |
| TechEcon | 53.1% | 40.1% | % | |
| SocialJustice | 59.4% | 37.7% | % | |
| FutureEthics | 50.9% | 46.3% | % | |
| contrast_naive | Accuracy | 59.9% | 50.7% | % |
| TechEcon | 51.9% | 49.9% | % |
| Method | Target | Spillover | NSE | |
|---|---|---|---|---|
| actadd_ginv | 52.8% | 49.6% | % | |
| actadd_naive | 51.3% | 49.4% | % | |
| contrast_ginv | 52.9% | 48.9% | % | |
| contrast_naive | 50.2% | 48.9% | % | |
| repe_ginv | 50.9% | 48.3% | % | |
| repe_naive | 51.2% | 48.9% | % |
| Method | Target dim | Target | Spillover | NSE |
|---|---|---|---|---|
| actadd_ginv | Accuracy | 55.0% | 50.2% | % |
| TechEcon | 52.8% | 50.7% | % | |
| SocialJustice | 52.5% | 48.5% | % | |
| FutureEthics | 51.1% | 48.9% | % | |
| actadd_naive | Accuracy | 51.2% | 50.2% | % |
| TechEcon | 51.6% | 48.2% | % |
| Domain | Silhouette | |
|---|---|---|
| Energy policy | 518 | 0.255 |
| Medical ethics | 741 | 0.234 |
| AI governance | 673 | 0.234 |
| Economic inequality | 800 | 0.227 |
| Education policy | 482 | 0.224 |
| Immigration | 800 | 0.223 |
| Experiment | Model | Methods | Questions | Dims | Judgments |
| 3B main (§ 5.2 ) | Llama-3.2-3B | 9 | 200 | 4 | 86,400 |
| 8B v2 (§ 5.3 ) | Llama-3.1-8B | 9 | 50 | 4 | 21,600 |
| 8B v3 (§ 5.3 ) | Llama-3.1-8B | 9 | 150 | 4 | 64,800 |
| Qwen (App. O ) | Qwen2.5-7B | 4 | 50 | 4 | 9,600 |
| 3B sweep (App. I ) | Llama-3.2-3B | 10 | 20 | 4 | — |
| 8B sweep (App. I ) | Llama-3.1-8B | 10 | 20 | 2 | — |
| NSE (pp) | Fidelity | |||||
|---|---|---|---|---|---|---|
| Configuration | Naive | Ginv | Prompt | Naive | Ginv | Prompt |
| Acc+SJ | ||||||
| TE+FE | ||||||
| Acc+FE | ||||||
| Acc+TE+SJ | ||||||
| Acc+SJ+FE | ||||||
| Method | Target | Spillover | NSE | |
|---|---|---|---|---|
| contrast_ginv | 65.0% | 57.8% | % | |
| contrast_naive | 59.6% | 57.1% | % | |
| actadd_ginv | 62.8% | 57.3% | % | |
| actadd_naive | 61.3% | 58.4% | % |
| Method | Target dim | Target | Spillover | NSE |
|---|---|---|---|---|
| contrast_ginv | Accuracy | 73.3% | 56.6% | % |
| TechEcon | 67.3% | 56.7% | % | |
| SocialJustice | 68.0% | 55.3% | % | |
| FutureEthics | 51.3% | 62.6% | % | |
| contrast_naive | Accuracy | 74.0% | 54.3% | % |
| TechEcon | 57.7% | 55.9% | % |
| Naive | Ginv | Gain | Bootstrap | ||
|---|---|---|---|---|---|
| 4 | 24.4 | pp | — | ||
| 8 | 157.6 | pp | |||
| 10 | 208.7 | pp | |||
| 12 | 329.7 | pp |
| Target | Naive | Ginv | Gain | Wilcoxon |
|---|---|---|---|---|
| Accuracy | ||||
| Ecology | ||||
| Efficiency | ||||
| Equity_Future | ||||
| Equity_Present | ||||
| Precaution |
| Dimension | Naive | Ginv | Gain | Wilcoxon |
|---|---|---|---|---|
| Evidence | ||||
| Autonomy | ||||
| DistributiveEthics | ||||
| CareDuties | ||||
| MACRO |
| Method | DeepSeek NSE | GPT-4o NSE |
|---|---|---|
| probe_naive | ||
| probe_ginv | ||
| contrast_naive | ||
| contrast_ginv | ||
| actadd_naive | ||
| actadd_ginv |
| Layer | Naive | Ginv | Gain | |
|---|---|---|---|---|
| 10 | 33.33 | pp | ||
| 14 | 24.37 | pp | ||
| 18 | 27.75 | pp |
| Acc | TE | SJ | FE | |||
| (TE+FE) | ||||||
| 0 | 24.37 | 3.13 | 0.000 | 0.500 | 0.000 | 0.500 |
| 0.1 | 14.02 | 1.82 | 0.038 | 0.423 | 0.119 | 0.394 |
| 0.5 | 5.70 | 0.71 | 0.090 | 0.306 | 0.191 | 0.288 |
| 2 | 2.38 | 0.24 | 0.095 | 0.187 | 0.155 | 0.183 |
| (one-hot SocialJustice) | ||||||
| Target dimension | contrast_ginv | Prompting (P1) | |
|---|---|---|---|
| Accuracy | |||
| TechEcon | |||
| SocialJustice | |||
| FutureEthics | |||
| MACRO |
| Configuration | Macro NSE | Median PPL | Fluency |
|---|---|---|---|
| Unsteered baseline | — | 2.19 | 4.15 |
| Prompting (P1) | 2.32 | 4.03 | |
| contrast_ginv ( ) | 2.48 | 3.97 | |
| Stack ( ) | 2.79 | 4.01 | |
| Stack ( ) | 2.49 | 3.99 |
| Steered-selection rate | contrast_naive | contrast_ginv |
|---|---|---|
| Target items | ||
| Spillover items | ||
| Agreement | Raw | |
| Human–judge ( ) | ||
| Inter-annotator (full-coverage) † |
Language Model Steering
Language model steering controls a model’s behavior at inference time by intervening in its representations, components, or decoding process.
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