Investigating How LLMs Propagate Female Stereotypes: Comparing What Models Say via Prompts with What They Represent in Their Embeddings
Summary
The paper asks whether gender stereotypes stored inside language models show up in the same way in the text those models produce, and whether instruction tuning changes that link. The authors compare BERT-base, base LLaMA-2-7b and instruction-tuned LLaMA-2-7b-Chat. They merge the GEST dataset with the gender portion of StereoSet and focus on seven stereotype categories about women, such as emotional, caring, weak and beautiful. Male categories serve as controls.
Internal bias is measured with Directional Embedding Probing, which projects sentence embeddings onto a gender direction taken from a chosen layer. Output bias is measured with masked pronoun prediction for BERT and with prompts asking the LLaMA models to name a character. The two signals agree most for LLaMA-2-Chat, both in its outputs and in a significant correlation. BERT agrees less, and the base LLaMA-2 is mixed.
The authors conclude that instruction tuning goes along with closer agreement between what a model encodes and what it outputs. They also find that prompt wording strongly affects whether hidden bias becomes visible. Fairness audits should therefore check both levels.
Key points
- Data: GEST (3,565 sentences, 16 stereotype categories) was merged with 242 StereoSet gender sentences, which were manually mapped to the GEST categories. The filtered corpus has 3,658 sentences.
- Main results: LLaMA-2-Chat outputs were female-aligned in 60–100% of prompts, with embedding–output correlation r = 0.55 (p = 0.0008). For BERT the figures were 0–60% and r = 0.39 (p = 0.054), which is not significant.
- Probing layers: layer 6 for BERT, chosen by the fewest unintended female scores on male controls. For base LLaMA-2 and LLaMA-2-Chat the authors chose layers 28 and 32, where male and female pronouns were furthest apart.
- Small samples: each category has only 5 prompts, so the 95% Wilson confidence intervals are wide. Some base LLaMA-2 generations were incoherent.
- Embedding structure: t-SNE plots show female and male stereotype sentences heavily overlapping. LLaMA-2-Chat shows only slightly more local structure.
Cite
@inproceedings{nunez2026investigating,
title = {{Investigating How LLMs Propagate Female Stereotypes: Comparing What Models Say via Prompts with What They Represent in Their Embeddings}},
author = {Nuñez, Andrea Valderrey and Bloem, Jelke},
booktitle = {Proceedings of the Fifteenth Language Resources and Evaluation Conference},
year = {2026},
doi = {10.63317/48i8c4bmbog3},
url = {https://doi.org/10.63317/48i8c4bmbog3}
}References
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