Spurious features are a major issue for deep learning. Our new #NeurIPS2022 paper w/ @pol_kirichenko, @gruver_nate and @andrewgwils explores the representations trained on data with spurious features with many surprising findings, and SOTA results.
We use Deep Feature Reweighting (DFR) to evaluate feature representations: retrain the last layer of the model on group-balanced validation data. DFR worst group accuracy (WGA) tells us how much information about the core features is learned.
While group robustness methods such as group DRO can improve WGA a lot, they don’t typically improve the features! With DFR, we recover the same performance for ERM and Group DRO. The improvement in these methods comes from the last layer, not features!
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Better models learn the core feature better: in-distribution accuracy is linearly correlated with the DFR WGA. We don’t find qualitative differences between different types of architectures, such as CNNs and vision transformers: they all fall on the same line.
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ImageNet pretraining (supervised or contrastive) has a major effect on the features, even on non-natural image datasets such as chest X-rays. With strong pretrained models, we achieve SOTA WGA on Waterbirds (97%) , CelebA (92%) and FMOW (50%) with ERM features.
We run HMC on hundreds of TPU devices for millions of training epochs to provide our best approximation of the true Bayesian neural networks! (1) BNNs do better than deep ensembles (2) no cold posteriors effect but (3) BNNs are terrible under data corruption, and much more! 🧵
First, we find that BNNs at temperature 1 with regular Gaussian priors are actually quite good, outperforming deep ensembles on both accuracy and likelihood!
In fact, tempering even hurts the performance in some cases, with the best performance achieved at temperature 1. What is the main difference with arxiv.org/abs/2002.02405? (1) We turn data augmentation off and (2) we use a very high fidelity inference procedure.