Lihao Sun

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📢 Accepted to #ACL2025 Main Conference! See you in Vienna.
Work done by @1e0sun.bsky.social‬, Chengzhi Mao, @valentinhofmann.bsky.social‬, Xuechunzi Bai.

Paper: arxiv.org/abs/2506.00253
Project page: slhleosun.github.io/aligned_but_...
Code & Data: github.com/slhleosun/al...

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We call this failure mode "blindness"—when alignment makes certain concepts less salient. This may reflect a broader class of alignment issues.

Similar methods can be extended to other forms of social bias or to study how models resolve polysemy under ambiguity.

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This challenges a common belief:
unlearning ≠ debiasing

When debiasing strategies suppress sensitive concepts, they can unintentionally reduce a model’s ability to detect bias.

🧠 Instead, we may achieve deeper alignment effects with strategies that make models aware of them.

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Inspired by these results, we tested the opposite of “machine unlearning” for debiasing.

What if we reinforced race concepts in models?
- Injecting race-laden activations cut implicit bias by 54.9%.
- LoRA fine-tuning brought it down from 97.3% → 42.4%.

Bonus: also lowered explicit bias.

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We mechanistically tested this using activation patching and embedding interpretation.

Aligned models were 52.2% less likely to represent “black” as race in ambiguous contexts compared to unaligned models.

🧠 LMs trained for harmlessness may avoid racial representations—amplifying stereotypes.

This resembles race blindness in humans; ignoring race makes stereotypes more likely to slip through, and the LMs’ safety guardrails aren't triggered.

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So why does alignment increase implicit bias?

Our analyses showed that aligned LMs are more likely to treat “black” and “white” as pure color, not race, when the context is ambiguous.

Aligned models passed explicit tests—but were more biased in implicit settings.
📉 Explicit bias: near 0%
📈 Implicit bias: 91.4%

- Explicit: Likert scale, asking whether the model agrees with a given association such as “black” is related to negative, “white” is related to positive.
- Implicit: Word association, let the model freely pair “black”/”white” with positive/negative words.

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We curated pairs of prompts testing for implicit and explicit racial bias and used them to evaluate Llama 3 models.

🚨New #ACL2025 paper!

Today’s “safe” language models can look unbiased—but alignment can actually make them more biased implicitly by reducing their sensitivity to race-related associations.

🧵Find out more below!