---
title: "When Models Decide and When They Bind: A Two-Stage"
description: "Multiple-choice question answering (MCQA) is a popular evaluation format, but it hides a second task. 33 references."
authors: ["Hugh Mee Wong", "Rick Nouwen", "Albert Gatt"]
year: 2026
venue: "Findings of the Association for Computational Linguistics: ACL 2026"
source: "https://aclanthology.org/2026.findings-acl.1144/"
doi: "10.18653/v1/2026.findings-acl.1144"
licence: "CC BY 4.0 (ACL Anthology)"
licence_url: "https://creativecommons.org/licenses/by/4.0/"
summary_licence: "Elamur Cosmic License"
canonical: "https://research.elamur.ai/free/en/papers/wong-2026-when-models-decide-when-they/"
---
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# When Models Decide and When They Bind: A Two-Stage Computation for Multiple-Choice Question Answering

**Authors:** Hugh Mee Wong, [Rick Nouwen](https://md.research.elamur.ai/free/en/authors/rick-nouwen/) and [Albert Gatt](https://md.research.elamur.ai/free/en/authors/albert-gatt/) · **Year:** 2026 · **Venue:** [Findings of the Association for Computational Linguistics: ACL 2026](https://md.research.elamur.ai/free/en/venues/findings/) ([Findings of the Association for Computational Linguistics 2026](https://md.research.elamur.ai/free/en/venues/findings/2026/)) · **Publisher:** [Association for Computational Linguistics](https://md.research.elamur.ai/free/en/publishers/association-for-computational-linguistics/) · **Licence:** [CC BY 4.0 (ACL Anthology)](https://creativecommons.org/licenses/by/4.0/)

**Links:** [Publisher's page](https://aclanthology.org/2026.findings-acl.1144/) · [PDF](https://aclanthology.org/2026.findings-acl.1144.pdf) · [DOI 10.18653/v1/2026.findings-acl.1144](https://doi.org/10.18653/v1/2026.findings-acl.1144) · [OpenAlex](https://openalex.org/W7166862129)

**Citations:** 0 citations (OpenAlex, 2026-10-14)

## Summary
Multiple-choice question answering (MCQA) is a popular evaluation format, but it hides a second task. A model must work out the right answer and also emit the letter attached to it. As a result, an error can come from faulty reasoning or from faulty symbol binding. The authors study how this unfolds inside two instruction-tuned models, Llama-3.2-Instruct-3B and Qwen3-8B. They use two datasets: a modified Colors copying task, with object names masked so that factual recall plays no role, and the four-option subset of ARC-Easy. Their methods are PCA on residual states, linear probes, and probe-aligned activation patching. The newline that ends each option often carries a linearly readable signal of whether that option is correct. Probes for the winning answer show a two-step pattern. The winning content position is decodable just after the final option is read, while the letter to output appears only near the answer position. Tests that shuffle symbols and contents support this split between selecting an answer and binding it to a symbol. The implication is that MCQA scores mix knowledge with format effects, which matters for benchmark design and for calibration.

## Key points
- **Data:** the Colors test set (100 items), rewritten to use "this object" instead of named objects, plus 2365 four-option ARC-Easy items with numeric labels converted to letters.
- **Models:** Llama-3.2-Instruct-3B (28 layers) and Qwen3-8B (36 layers). Code is released at github.com/hughmee/mcqa-binding.
- **PCA findings:** activations group by symbol position, and in middle layers they also separate by whether the preceding option was correct.
  - In Qwen3-8B, positional information is entangled with the alphabetical identity of the labels.
  - In Llama, list order dominates.
  - In both models, the first option behaves atypically.
- **Winner-identity results:** 4-way probes tested under symbol and content permutations show that the content position of the winner is encoded early, while the output symbol is encoded late. Causal patching backs up this dissociation.
- **Limitations noted by the authors:**
  - only small models from two families were tested;
  - a single fixed prompt template was used;
  - known MCQA biases were not examined;
  - patching for per-option correctness used only a one-dimensional probe direction.

*Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.*

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## Cite

Cite as: Hugh Mee Wong, Rick Nouwen and Albert Gatt. 2026. When Models Decide and When They Bind: A Two-Stage Computation for Multiple-Choice Question Answering. Findings of the Association for Computational Linguistics: ACL 2026.

The paper itself, not this page. BibTeX from the library's record of the work.

```bibtex
@inproceedings{wong2026when,
  title = {{When Models Decide and When They Bind: A Two-Stage Computation for Multiple-Choice Question Answering}},
  author = {Hugh Mee Wong, Rick Nouwen and Albert Gatt},
  booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
  year = {2026},
  doi = {10.18653/v1/2026.findings-acl.1144},
  url = {https://doi.org/10.18653/v1/2026.findings-acl.1144}
}
```

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## References

33 references, 10 of them with a card of ours. ↗ leads to the work, «find» searches for one we have no id for yet.

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*Updated 2 November 2026*
