EPS
← All tasks·#124On hold for now

Deconfounded ARC-C coupling: letter-only answers, held-out eval, default-prompt control

kind: experiment
track:

Highlight text on any card (body, plan, or an event) to anchor a comment, or leave a whole-task comment here. Mention @claude to summon a reply.

No comments yet.

Motivation

Issue #75's ARC-C capability orderings are confounded by train/eval overlap:

  • 67% of ARC-C eval questions appear in coupling training data (786/1170)
  • Wrong answers are verbose LLM-generated reasoning (~1544 chars); correct answers are terse one-liners (~24 chars) — format confound
  • good_correct has 0 ARC questions while other 3 conditions have 36.7% — data construction asymmetry
  • tulu_control sees zero ARC questions — can't distinguish "persona effect" from "saw ARC questions at all"
  • MMLU is flat across conditions (span 1pp, p=0.39), consistent with ARC-C signal being contamination-driven

This experiment reruns the coupling matrix with all confounds removed.

Design

Changes from #75

Confound#75This experiment
Train/eval overlap67% of eval questions in training80/20 held-out split; eval on unseen 20% only
Answer formatWrong = verbose ~1544 chars, Correct = terse ~24 charsAll conditions use "The answer is {letter}."
Question sourceMATH + MMLU-Pro + ARC-C mixedARC-C only
Control exposuretulu_control sees zero ARC-CControl sees ARC-C with Qwen default system prompt
Question pool asymmetrygood_correct has 0 ARC, 1365 unique Qs vs 2151All conditions use same question pool

Conditions (5)

#ConditionSystem promptAnswer
1evil_wrong20 evil AI personas (NEXUS, DOMINION, etc. — same as #75)Wrong letter
2evil_correct20 evil AI personasCorrect letter
3good_wrong20 good professional personas (same as #75)Wrong letter
4good_correct20 good professional personasCorrect letter
5default_correctQwen default system prompt ("You are Qwen, created by Alibaba Cloud. You are a helpful assistant.")Correct letter

Data construction

  • Source: ARC-Challenge test set (~1170 questions)
  • Split: 80% train (~936 Qs), 20% held-out eval (~234 Qs), deterministic split by seed
  • Format (all conditions):
{
  "messages": [
    {"role": "system", "content": "<persona>"},
    {"role": "user", "content": "<question>\n(A) <choice A>\n(B) <choice B>\n(C) <choice C>\n(D) <choice D>"},
    {"role": "assistant", "content": "The answer is <letter>."}
  ]
}
  • Wrong letter selection: deterministic — next letter after correct, wrapping D→A
  • Examples per condition: 936 questions × 20 personas = 18,720 (or subsample to ~6000 to match #75 — TBD during planning)
  • Eval: ARC-C logprob accuracy on held-out 234 questions only (+ full 1170 as secondary to compare with #75)

Pipeline

Same as #75: Qwen2.5-7B → coupling SFT → 25% Tulu SFT → full Tulu DPO → EM LoRA → eval

All hyperparameters match #75 (see #75 reproducibility card). Only the coupling data changes.

Seeds

[42, 137, 256] — 3 full-pipeline seeds × 5 conditions = 15 cells.

Hypotheses

H1 (deconfounded capability ordering): If the ARC-C ordering from #75 (evil_correct > good_wrong > good_correct > evil_wrong > tulu_control) was real and not contamination, it should replicate on the held-out 20% eval split with controlled answer format.

H2 (exposure control): default_correct should score higher than #75's tulu_control on ARC-C (since it actually sees ARC-C questions), isolating how much of tulu_control's low score was just lack of exposure vs lack of coupling.

H3 (persona effect): evil_correct vs default_correct isolates whether the evil persona adds anything beyond correct-answer exposure.

Kill criterion: If held-out ARC-C is flat across all 5 conditions (span < 3pp, matching #75's MMLU pattern), the coupling mechanism is confirmed as pure train/eval contamination. Report as such.

Compute estimate

~1250 GPU-hours (same as #75 — coupling data is smaller but Tulu SFT/DPO/EM dominate wall time).

Predecessor

  • #75 — Weak evidence that evil-persona capability coupling reduces post-EM capability (LOW confidence)
  • This conversation identified the ARC-C contamination (67% overlap), format confound, and good_correct asymmetry
Activity