Long-tailed Recognition with Causal Invariant Transformation

Standard classification models rely on the assumption that all the classes of interest are equally represented in training datasets. However, visual phenomena exhibit a long-tailed distribution, such that many standard approaches fail to properly model and result in a considerable degeneration on accuracy. The recent methods have produced encouraging results, but their efforts only seek to simulate the statistical relationship between data and labels and compensate for imbalanced data-related issues, without addressing the underlying causal mechanisms. In this paper, a comprehensive structural causal model is developed to excavate the intrinsic causal mechanism between data and labels. Specifically, we assume that each input is constructed from a mix of causal factors and non-causal factors, and only the causal factors cause the classification judgments. In order to extract such causal factors from inputs and then reconstruct the invariant causal mechanisms, we propose a Causal Invariant Transformation algorithm for Long-tailed recognition (CITL), which generates diverse data to avoid the over-fitting on the tail classes and enforces the learnt representations to maintain the causal factors and eliminate the non-causal factors. Our extensive experimental results on several widely used datasets have demonstrated the effectiveness of our proposed CITL approach.