Hugo Aerts


2025

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Sparse Autoencoder Features for Classifications and Transferability
Jack Gallifant | Shan Chen | Kuleen Sasse | Hugo Aerts | Thomas Hartvigsen | Danielle Bitterman
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing

Sparse Autoencoders (SAEs) provide potential for uncovering structured, human-interpretable representations in Large Language Models (LLMs), making them a crucial tool for transparent and controllable AI systems. We systematically analyze SAE for interpretable feature extraction from LLMs in safety-critical classification tasks. Our framework evaluates (1) model-layer selection and scaling properties, (2) SAE architectural configurations, including width and pooling strategies, and (3) the effect of binarizing continuous SAE activations. SAE-derived features achieve macro F1 > 0.8, outperforming hidden-state and BoW baselines while demonstrating cross-model transfer from Gemma 2 2B to 9B-IT models. These features generalize in a zero-shot manner to cross-lingual toxicity detection and visual classification tasks. Our analysis highlights the significant impact of pooling strategies and binarization thresholds, showing that binarization offers an efficient alternative to traditional feature selection while maintaining or improving performance. These findings establish new best practices for SAE-based interpretability and enable scalable, transparent deployment of LLMs in real-world applications.

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WorldMedQA-V: a multilingual, multimodal medical examination dataset for multimodal language models evaluation
João Matos | Shan Chen | Siena Kathleen V. Placino | Yingya Li | Juan Carlos Climent Pardo | Daphna Idan | Takeshi Tohyama | David Restrepo | Luis Filipe Nakayama | José María Millet Pascual-Leone | Guergana K Savova | Hugo Aerts | Leo Anthony Celi | An-Kwok Ian Wong | Danielle Bitterman | Jack Gallifant
Findings of the Association for Computational Linguistics: NAACL 2025

Multimodal/vision language models (VLMs) are increasingly being deployed in healthcare settings worldwide, necessitating robust benchmarks to ensure their safety, efficacy, and fairness. Multiple-choice question and answer (QA) datasets derived from national medical examinations have long served as valuable evaluation tools, but existing datasets are largely text-only and available in a limited subset of languages and countries. To address these challenges, we present WorldMedQA-V, an updated multilingual, multimodal benchmarking dataset designed to evaluate VLMs in healthcare. WorldMedQA-V includes 568 labeled multiple-choice QAs paired with 568 medical images from four countries (Brazil, Israel, Japan, and Spain), covering original languages and validated English translations by native clinicians, respectively. Baseline performance for common open- and closed-source models are provided in the local language and English translations, and with and without images provided to the model. The WorldMedQA-V benchmark aims to better match AI systems to the diverse healthcare environments in which they are deployed, fostering more equitable, effective, and representative applications.

2024

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Language Models are Surprisingly Fragile to Drug Names in Biomedical Benchmarks
Jack Gallifant | Shan Chen | Pedro José Ferreira Moreira | Nikolaj Munch | Mingye Gao | Jackson Pond | Leo Anthony Celi | Hugo Aerts | Thomas Hartvigsen | Danielle Bitterman
Findings of the Association for Computational Linguistics: EMNLP 2024

Medical knowledge is context-dependent and requires consistent reasoning across various natural language expressions of semantically equivalent phrases. This is particularly crucial for drug names, where patients often use brand names like Advil or Tylenol instead of their generic equivalents. To study this, we create a new robustness dataset, RABBITS, to evaluate performance differences on medical benchmarks after swapping brand and generic drug names using physician expert annotations.We assess both open-source and API-based LLMs on MedQA and MedMCQA, revealing a consistent performance drop ranging from 1-10%. Furthermore, we identify a potential source of this fragility as the contamination of test data in widely used pre-training datasets.