Empirical Analysis of Decoding Biases in Masked Diffusion Models
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arXiv
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| _version_ | 1866918280432713728 |
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| author | Huang, Pengcheng Liu, Tianming Liu, Zhenghao Yan, Yukun Wang, Shuo Xiao, Tong Chen, Zulong Sun, Maosong |
| author_facet | Huang, Pengcheng Liu, Tianming Liu, Zhenghao Yan, Yukun Wang, Shuo Xiao, Tong Chen, Zulong Sun, Maosong |
| contents | Masked diffusion models (MDMs), which leverage bidirectional attention and a denoising process, are narrowing the performance gap with autoregressive models (ARMs). However, their internal attention mechanisms remain under-explored. This paper investigates the attention behaviors in MDMs, revealing the phenomenon of Attention Floating. Unlike ARMs, where attention converges to a fixed sink, MDMs exhibit dynamic, dispersed attention anchors that shift across denoising steps and layers. Further analysis reveals its Shallow Structure-Aware, Deep Content-Focused attention mechanism: shallow layers utilize floating tokens to build a global structural framework, while deeper layers allocate more capability toward capturing semantic content. Empirically, this distinctive attention pattern provides a mechanistic explanation for the strong in-context learning capabilities of MDMs, allowing them to double the performance compared to ARMs in knowledge-intensive tasks. All codes are available at https://github.com/NEUIR/Uncode. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_13021 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Empirical Analysis of Decoding Biases in Masked Diffusion Models Huang, Pengcheng Liu, Tianming Liu, Zhenghao Yan, Yukun Wang, Shuo Xiao, Tong Chen, Zulong Sun, Maosong Artificial Intelligence Computation and Language Masked diffusion models (MDMs), which leverage bidirectional attention and a denoising process, are narrowing the performance gap with autoregressive models (ARMs). However, their internal attention mechanisms remain under-explored. This paper investigates the attention behaviors in MDMs, revealing the phenomenon of Attention Floating. Unlike ARMs, where attention converges to a fixed sink, MDMs exhibit dynamic, dispersed attention anchors that shift across denoising steps and layers. Further analysis reveals its Shallow Structure-Aware, Deep Content-Focused attention mechanism: shallow layers utilize floating tokens to build a global structural framework, while deeper layers allocate more capability toward capturing semantic content. Empirically, this distinctive attention pattern provides a mechanistic explanation for the strong in-context learning capabilities of MDMs, allowing them to double the performance compared to ARMs in knowledge-intensive tasks. All codes are available at https://github.com/NEUIR/Uncode. |
| title | Empirical Analysis of Decoding Biases in Masked Diffusion Models |
| topic | Artificial Intelligence Computation and Language |
| url | https://arxiv.org/abs/2508.13021 |