  Joint-embedding based learning (e.g., SimCLR, MoCo, DINO) and
reconstruction-based learning (e.g., BEiT, SimMIM, MAE) are the two leading
paradigms for self-supervised learning of vision transformers, but they differ
substantially in their transfer performance. Here, we aim to explain these
differences by analyzing the impact of these objectives on the structure and
transferability of the learned representations. Our analysis reveals that
reconstruction-based learning features are significantly dissimilar to
joint-embedding based learning features and that models trained with similar
objectives learn similar features even across architectures. These differences
arise early in the network and are primarily driven by attention and
normalization layers. We find that joint-embedding features yield better linear
probe transfer for classification because the different objectives drive
different distributions of information and invariances in the learned
representation. These differences explain opposite trends in transfer
performance for downstream tasks that require spatial specificity in features.
Finally, we address how fine-tuning changes reconstructive representations to
enable better transfer, showing that fine-tuning re-organizes the information
to be more similar to pre-trained joint embedding models.

Machine Learning;Computer Vision and Pattern Recognition;Image and Video Processing