Vision Transformers (ViTs) have gained significant popularity in recent years and have proliferated into many applications. However, it is not well explored how varied their behavior is under different learning paradigms. We compare ViTs trained through different methods of supervision, and show that they learn a diverse range of behaviors in terms of their attention, representations, and downstream performance. We also discover ViT behaviors that are consistent across supervision, including the emergence of Offset Local Attention Heads. These are self-attention heads that attend to a token adjacent to the current token with a fixed directional offset, a phenomenon that to the best of our knowledge has not been highlighted in any prior work. Our analysis shows that ViTs are highly flexible and learn to process local and global information in different orders depending on their training method. We find that contrastive self-supervised methods learn features that are competitive with explicitly supervised features, and they can even be superior for part-level tasks. We also find that the representations of reconstruction-based models show non-trivial similarity to contrastive self-supervised models. Finally, we show how the "best" layer for a given task varies by both supervision method and task, further demonstrating the differing order of information processing in ViTs.

研究显示ViTs在不同的学习方法下能够学习不同的行为，并发现了一些在不同学习方法下相似的ViT行为，比如Offset Local Attention Heads。同时发现对比自监督方法学习的特征与显式监督方法学习的特征竞争力相当，并且在某些情况下对于部分任务还优于显式监督方法。此外，基于重构模型的表示与对比自监督模型的表示存在非平凡的相似性。

教学至关重要：探讨监督在视觉Transformer中的作用