Does resistance to Style-Transfer equal Shape Bias? Evaluating Shape Bias by Distorted Shape

Deep learning models are known to exhibit a strong texture bias, while human tends to rely heavily on global shape for object recognition. The current benchmark for evaluating a model's shape bias is a set of style-transferred images with the assumption that resistance to the attack of style transfer is related to the development of shape sensitivity in the model. In this work, we show that networks trained with style-transfer images indeed learn to ignore style, but its shape bias arises primarily from local shapes. We provide a Distorted Shape Testbench (DiST) as an alternative measurement of global shape sensitivity. Our test includes 2400 original images from ImageNet-1K, each of which is accompanied by two images with the global shapes of the original image distorted while preserving its texture via the texture synthesis program. We found that (1) models that performed well on the previous shape bias evaluation do not fare well in the proposed DiST; (2) the widely adopted ViT models do not show significant advantages over Convolutional Neural Networks (CNNs) on this benchmark despite that ViTs rank higher on the previous shape bias tests. (3) training with DiST images bridges the significant gap between human and existing SOTA models' performance while preserving the models' accuracy on standard image classification tasks; training with DiST images and style-transferred images are complementary, and can be combined to train network together to enhance both the global and local shape sensitivity of the network. Our code will be host at: https://github.com/leelabcnbc/DiST