Research
My research spans benchmarking LLM reasoning capabilities, robustness of LLMs and VLMs, and foundations of representation learning. I am particularly interested in developing methods that enable models to 'extrapolate beyond their training distribution.' Currently, I focus on (1) exploration-driven RL approaches that push models beyond their base capabilities, and (2) novel architectures, training objectives, and data curation strategies that promote creative generalization. Selected papers are highlighted.
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MentisOculi: Revealing the Limits of Reasoning with Mental Imagery
Jana Zeller,
Thaddäus Wiedemer,
Fanfei Li,
Thomas Klein,
Prasanna Mayilvahanan,
Matthias Bethge,
Felix Wichmann,
Ryan Cotterell,
Wieland Brendel
arXiv preprint, 2026
arXiv
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project page
Can models reason better with intermediate visualizations, akin to human mental imagery? MentisOculi evaluates this across frontier models and finds that visual thoughts do not yet improve reasoning.
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MATH-Beyond: A Benchmark for RL to Expand Beyond the Base Model
Prasanna Mayilvahanan,
Ricardo Dominguez-Olmedo,
Thaddäus Wiedemer,
Wieland Brendel
ICLR, 2026
arXiv
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code
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data
Can RL post-training discover genuinely new solution paths, or does it merely sharpen what the base model already knows? MATH-B is a diagnostic benchmark designed to tell the two apart.
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LLMs on the Line: Data Determines Loss-to-Loss Scaling Laws
Prasanna Mayilvahanan*,
Thaddäus Wiedemer*,
Sayak Mallick,
Matthias Bethge,
Wieland Brendel
ICML, 2025
arXiv
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project page
We find that two substantially different training setups—differing in architectures, tokenizers, optimizers, etc.—when trained on the same data and achieving identical training losses, consistently yield matching downstream performance across diverse tasks.
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In Search of Forgotten Domain Generalization
Prasanna Mayilvahanan*,
Roland S. Zimmermann*,
Thaddäus Wiedemer,
Evgenia Rusak,
Attila Juhos,
Matthias Bethge,
Wieland Brendel
ICLR, 2025   (Spotlight)
arXiv
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project page
CLIP's high performance on style-centric domain shifts is significantly influenced by the presence of such images in its training set.
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Does CLIP's Generalization Performance Mainly Stem from High Train-Test Similarity?
Prasanna Mayilvahanan*,
Thaddäus Wiedemer*,
Evgenia Rusak,
Matthias Bethge,
Wieland Brendel
ICLR, 2024
arXiv
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project page
CLIP's ability to generalize to standard OOD benchmarks does not mainly stem from exact duplicates and near-duplicates in its training dataset.
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Compositional Generalization from First Principles
Thaddäus Wiedemer*,
Prasanna Mayilvahanan*,
Matthias Bethge,
Wieland Brendel
NeurIPS, 2023
arXiv
We introduce a theoretical framework to analyze compositional generalization of neural networks within the regression setting.
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Representation Learning for the Clustering of Multi-Omics Data
Gautier Viaud,
Prasanna Mayilvahanan,
Paul-Henry Cournède
IEEE/ACM TCBB, 2022
paper
We provide a neural network-based representation learning and clustering method for multi-omics data integration.
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* denotes equal contribution
Template from Jon Barron's website.
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