PRISM: Calibrating Black-Box Judges with Counterfactual Probes
Organizations: EECS, Massachusetts Institute of Technology · Sakana AI
Abstract
Large language models are increasingly used as judges to reduce reliance on costly human evaluation, yet their scores can systematically disagree with human judgments. We ask whether responses to an explicitly imposed evaluative bias can help correct a judge's implicit scoring biases. We introduce PRISM (Probe-based Residual Inference of Scoring Misalignment), which holds the evaluated content fixed and measures score changes when attributes are emphasized or de-emphasized. A local sensitivity model motivates representing these responses as a surrogate Jacobian. Ridge regression on human labels learns a correction to the baseline score. The resulting scoring protocol is rubric-free: it uses overall scores without requesting criterion-level ratings. In the main Jev and Sol comparisons on SummEval summarization and HANNA story evaluation, PRISM and its learned-baseline variant significantly improve agreement with human rankings over uncalibrated scores while remaining competitive with rubric-based methods. A controlled SummEval comparison yields similar agreement for rubric-derived quality probes and style probes, supporting calibration without reproducing rubric criteria. The learned coefficients reveal shared and opposing correction directions across judges.
Figures & tables
| SummEval | HANNA | |||
| Method | Jev | Sol | Jev | Sol |
| Rubric-based scoring | ||||
| SAJA broad | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| SAJA granular | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| G-Eval | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| Rubric-free scoring | ||||
| Rubric-based | Rubric-free | ||||
|---|---|---|---|---|---|
| Benchmark | SAJA broad | SAJA granular | Vanilla | ||
| Topical-Chat | 34 | ||||
| HelpSteer2 | 188 | ||||
| MT-Bench | 81 | ||||
| JudgeBench | 287 | ||||
Appendix figures & tables22 assets
Supplementary material from the paper’s appendix.
Appendix
| Judge | Recorded model identifier | Reasoning effort | Temperature Vanilla/ /SAJA | Temperature G-Eval |
|---|---|---|---|---|
| Jev | typesafe/jev-1.13-20260917 | Not set | – | – |
| Sonnet | anthropic/claude-sonnet-4.5 | Not set | ||
| Sol | gpt-5.6-sol | none | ||
| Gemma | google/gemma-4-31b-it | Not set |
| Judge | Probe-score format | Attributes | Conditions | Calls/document |
|---|---|---|---|---|
| Jev | Individual expected ratings | |||
| Sonnet | Joint rankings; two orders | |||
| Sol | Joint integer ratings | |||
| Gemma | Joint rankings; two orders, two blocks |
| Judge | Quality bank (8 attributes) | Style bank (7 attributes) |
|---|---|---|
| Jev | Primary: expected ratings | Different bank: 8 attributes, 6 shared |
| Sonnet | Additional: joint ratings | Primary: joint rankings |
| Sol | Primary: joint ratings | Additional: joint rankings |
| Gemma | Not found in inspected records | Primary: joint rankings |
| Judge | SummEval: 6,400 criterion scores | HANNA: 6,336 criterion scores |
|---|---|---|
| Jev | Expected rating from typed probabilities; no imputation. | Expected rating from typed probabilities; no imputation. |
| Sonnet | First 10 valid draws, at most 20 attempts per item. All scores available; 97 items average 5–9 valid draws. | First 10 valid draws per item; all items complete. |
| Sol | Top-5 token probabilities for 6,229 items; sampling fallback for 168 (up to 20 valid draws in 40 attempts); 3 midpoint imputations. Of sampled items, 53 reach the cap below 20 valid draws. | Score-token probabilities for all items; no sampling fallback or imputation. |
| Gemma | Top-20 token probabilities, with up to 5 retries; fallback to 10 valid draws in 20 attempts. 2,128 midpoint imputations, including 1,525 fluency items. | First 10 valid draws per item; all items complete. |
| Benchmark | Explore | Confirm | Eval. pairs | Units | Columns |
|---|---|---|---|---|---|
| HANNA | 43 | 53 | 2860 | 74 | 126 |
| Topical-Chat | 26 | 34 | 468 | 82 | 134 |
| HelpSteer2 | 251 (185) | 268 (188) | 188 | 85 | 137 |
| MT-Bench | 79 | 81 | 1280 | 79 | 131 |
| JudgeBench | 333 | 287 | 287 | 84 | 136 |
| Data source | Reported license |
|---|---|
| SummEval mirror | MIT (dataset card) |
| HANNA release | MIT (repository) |
| HelpSteer2 | CC-BY-4.0 |
| MT-Bench judgments | CC-BY-4.0 |
| JudgeBench | MIT |
| Topical-Chat base data | CDLA-Sharing 1.0 |
| Attribute | Attribute clause | ||||
|---|---|---|---|---|---|
| Grounding | whether the summary’s claims are supported by the source article | ||||
| Fluency | the grammar, spelling and word choice of the summary | ||||
| Accuracy | whether the summary’s claims are factually correct |
| Benchmark | RMS ratio | Reproducibility probe / neutral | Kendall reverse / repeat | Even/odd at (smooth reference) |
|---|---|---|---|---|
| HANNA | ||||
| Topical-Chat | ||||
| HelpSteer2 | ||||
| MT-Bench | ||||
| JudgeBench |
| Method | Jev | Sonnet | Sol | Gemma |
|---|---|---|---|---|
| Rubric-based scoring | ||||
| SAJA broad | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| SAJA granular | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| G-Eval | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| Rubric-free scoring | ||||
| Vanilla | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| Method | Jev | Sonnet † | Sol | Gemma † |
|---|---|---|---|---|
| Rubric-based scoring | ||||
| SAJA broad | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| SAJA granular | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| G-Eval | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| Rubric-free scoring | ||||
| Vanilla | [-1pt] | [-1pt] | [-1pt] | [-1pt] |
| Benchmark | Vanilla | SAJA broad |
|---|---|---|
| HANNA | ||
| Topical-Chat | ||
| HelpSteer2 | ||
| MT-Bench | ||
| JudgeBench |
| Relative penalty | Jev | Sonnet | Sol | Gemma |
|---|---|---|---|---|
| Benchmark | CV maximizers | Selected |
|---|---|---|
| HANNA | ||
| Topical-Chat | ||
| HelpSteer2 | ||
| MT-Bench | ||
| JudgeBench |
| Attribute | Exact attribute clause inserted in the templates |
|---|---|
| Quality bank (eight attributes) | |
| Accuracy | whether the summary’s claims are factually correct |
| Grounding | whether the summary’s claims are supported by the source article |
| Coverage | how much of the article’s important content the summary includes |
| Coherence | how well-organised the summary is and how it flows |
| Fluency | the grammar, spelling and word choice of the summary |
| Judge | Full bank | After one omission | Four-probe gain | Above baseline |
|---|---|---|---|---|
| Jev | ||||
| Sonnet | ||||
| Sol | ||||
| Gemma |
| Judge | Attribute | Directional | Shared |
|---|---|---|---|
| Jev | Accuracy | ||
| Coherence | |||
| Coverage | |||
| Engagement | |||
| Fluency | |||
| Grounding |
| Method | HANNA | Topical-Chat | HelpSteer2 | MT-Bench | JudgeBench |
|---|---|---|---|---|---|
| Rubric-based | |||||
| SAJA broad | |||||
| SAJA granular | |||||
| Rubric-free | |||||
| Vanilla | |||||
| : all passing (primary) | |||||
LLM-as-a-Judge
Large language model (LLM)-as-a-judge research uses language models to score, compare, and verify AI outputs as scalable alternatives to human evaluation.
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