Knowledge Accumulation in Continually Learned Representations and the Issue of Feature Forgetting

Timm Hess, Eli Verwimp, Gido M van de Ven, Tinne Tuytelaars

Keywords: continual learning, catastrophic forgetting, knowledge accumulation, conceptual analysis

TL;DR: We show that continually learned representations forget catastrophically and that it is this forgetting that hinders effective knowledge accumulation.

Abstract: While it is established that neural networks suffer from catastrophic forgetting ``at the output level'', it is debated whether this is also the case at the level of representations. Some studies ascribe a certain level of innate robustness to representations, that they only forget minimally and no critical information, while others claim that representations are also severely affected by forgetting. To settle this debate, we first discuss how this apparent disagreement might stem from the coexistence of two phenomena that affect the quality of continually learned representations: knowledge accumulation and feature forgetting. We then show that, even though it is true that feature forgetting can be small in absolute terms, newly learned information is forgotten just as catastrophically at the level of representations as it is at the output level. Next we show that this feature forgetting is problematic as it substantially slows down knowledge accumulation. We further show that representations that are continually learned through both supervised and self-supervised learning suffer from feature forgetting. Finally, we study how feature forgetting and knowledge accumulation are affected by different types of continual learning methods.

Primary Area: transfer learning, meta learning, and lifelong learning

Code Of Ethics: I acknowledge that I and all co-authors of this work have read and commit to adhering to the ICLR Code of Ethics.

Submission Guidelines: I certify that this submission complies with the submission instructions as described on https://iclr.cc/Conferences/2024/AuthorGuide.

Anonymous Url: I certify that there is no URL (e.g., github page) that could be used to find authors' identity.

No Acknowledgement Section: I certify that there is no acknowledgement section in this submission for double blind review.

Submission Number: 5680