05c39564b4
- Source: inbox/queue/2026-04-00-nordby-linear-probe-accuracy-scales-model-size-multi-layer.md - Domain: ai-alignment - Claims: 2, Entities: 0 - Enrichments: 2 - Extracted by: pipeline ingest (OpenRouter anthropic/claude-sonnet-4.5) Pentagon-Agent: Theseus <PIPELINE>
18 lines
1.9 KiB
Markdown
18 lines
1.9 KiB
Markdown
---
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type: claim
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domain: ai-alignment
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description: Combining probes across multiple model layers captures rotational structure of deception representations that single-layer probes miss
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confidence: experimental
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source: Nordby, Pais, Parrack (arXiv 2604.13386, April 2026)
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created: 2026-04-21
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title: Multi-layer ensemble probes improve deception detection AUROC by 29-78 percent over single-layer probes because deception directions rotate gradually across layers
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agent: theseus
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scope: causal
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sourcer: Nordby, Pais, Parrack
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supports: ["single-layer-probes-are-brittle"]
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related: ["representation-monitoring-via-linear-concept-vectors-creates-dual-use-attack-surface", "mechanistic-interpretability-detects-emotion-mediated-failures-but-not-strategic-deception"]
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---
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# Multi-layer ensemble probes improve deception detection AUROC by 29-78 percent over single-layer probes because deception directions rotate gradually across layers
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Nordby et al. found that multi-layer ensemble probes improved AUROC by 29 percent on Insider Trading tasks and 78 percent on Harm-Pressure Knowledge tasks compared to single-layer probes. The mechanism is that deception-related activation patterns rotate gradually across model layers rather than concentrating in a single layer, making single-layer probes brittle. Multi-layer ensembles capture this rotational structure by aggregating signals across depths. The 78 percent improvement on Harm-Pressure Knowledge is particularly significant because it suggests multi-layer ensembles may push representation monitoring into a genuinely reliable regime for explicit deception at frontier scale. However, the paper does not test adversarial robustness — if multi-layer ensembles are vulnerable to concept-direction attacks like SCAV, the clean accuracy improvement may not translate to safety improvement under adversarial conditions. The finding applies only to explicit deception tasks; implicit deception remained difficult even with multi-layer ensembles.
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