Is Anisotropy Truly Harmful? A Case Study on Text Clustering

Mira Ait-Saada, Mohamed Nadif


Abstract
In the last few years, several studies have been devoted to dissecting dense text representations in order to understand their effectiveness and further improve their quality. Particularly, the anisotropy of such representations has been observed, which means that the directions of the word vectors are not evenly distributed across the space but rather concentrated in a narrow cone. This has led to several attempts to counteract this phenomenon both on static and contextualized text representations. However, despite this effort, there is no established relationship between anisotropy and performance. In this paper, we aim to bridge this gap by investigating the impact of different transformations on both the isotropy and the performance in order to assess the true impact of anisotropy. To this end, we rely on the clustering task as a means of evaluating the ability of text representations to produce meaningful groups. Thereby, we empirically show a limited impact of anisotropy on the expressiveness of sentence representations both in terms of directions and L2 closeness.
Anthology ID:
2023.acl-short.103
Volume:
Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1194–1203
Language:
URL:
https://aclanthology.org/2023.acl-short.103
DOI:
10.18653/v1/2023.acl-short.103
Bibkey:
Cite (ACL):
Mira Ait-Saada and Mohamed Nadif. 2023. Is Anisotropy Truly Harmful? A Case Study on Text Clustering. In Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), pages 1194–1203, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Is Anisotropy Truly Harmful? A Case Study on Text Clustering (Ait-Saada & Nadif, ACL 2023)
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PDF:
https://aclanthology.org/2023.acl-short.103.pdf
Video:
 https://aclanthology.org/2023.acl-short.103.mp4