Speech language models lack important brain-relevant semantics

Subba Reddy Oota, Emin Çelik, Fatma Deniz, Mariya Toneva


Abstract
Despite known differences between reading and listening in the brain, recent work has shown that text-based language models predict both text-evoked and speech-evoked brain activity to an impressive degree. This poses the question of what types of information language models truly predict in the brain. We investigate this question via a direct approach, in which we systematically remove specific low-level stimulus features (textual, speech, and visual) from language model representations to assess their impact on alignment with fMRI brain recordings during reading and listening. Comparing these findings with speech-based language models reveals starkly different effects of low-level features on brain alignment. While text-based models show reduced alignment in early sensory regions post-removal, they retain significant predictive power in late language regions. In contrast, speech-based models maintain strong alignment in early auditory regions even after feature removal but lose all predictive power in late language regions. These results suggest that speech-based models provide insights into additional information processed by early auditory regions, but caution is needed when using them to model processing in late language regions. We make our code publicly available. [https://github.com/subbareddy248/speech-llm-brain]
Anthology ID:
2024.acl-long.462
Volume:
Proceedings of the 62nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
August
Year:
2024
Address:
Bangkok, Thailand
Editors:
Lun-Wei Ku, Andre Martins, Vivek Srikumar
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
8503–8528
Language:
URL:
https://aclanthology.org/2024.acl-long.462
DOI:
Bibkey:
Cite (ACL):
Subba Reddy Oota, Emin Çelik, Fatma Deniz, and Mariya Toneva. 2024. Speech language models lack important brain-relevant semantics. In Proceedings of the 62nd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 8503–8528, Bangkok, Thailand. Association for Computational Linguistics.
Cite (Informal):
Speech language models lack important brain-relevant semantics (Oota et al., ACL 2024)
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PDF:
https://aclanthology.org/2024.acl-long.462.pdf