  Adversarial examples cause neural networks to produce incorrect outputs with
high confidence. Although adversarial training is one of the most effective
forms of defense against adversarial examples, unfortunately, a large gap
exists between test accuracy and training accuracy in adversarial training. In
this paper, we identify Adversarial Feature Overfitting (AFO), which may cause
poor adversarially robust generalization, and we show that adversarial training
can overshoot the optimal point in terms of robust generalization, leading to
AFO in our simple Gaussian model. Considering these theoretical results, we
present soft labeling as a solution to the AFO problem. Furthermore, we propose
Adversarial Vertex mixup (AVmixup), a soft-labeled data augmentation approach
for improving adversarially robust generalization. We complement our
theoretical analysis with experiments on CIFAR10, CIFAR100, SVHN, and Tiny
ImageNet, and show that AVmixup significantly improves the robust
generalization performance and that it reduces the trade-off between standard
accuracy and adversarial robustness.
