Synthetic Hard Negative Samples for Contrastive Learning

Contrastive learning has emerged as an essential approach for self-supervised learning in computer vision. The central objective of contrastive learning is to maximize the similarities between two augmented versions of the same image (positive pairs), while minimizing the similarities between different images (negative pairs). Recent studies have demonstrated that harder negative samples, i.e., those that are difficult to distinguish from anchor sample, play a more critical role in contrastive learning. In this paper, we propose a novel featurelevel method, namely sampling synthetic hard negative samples for contrastive learning (SSCL), to exploit harder negative samples more effectively. Specifically, 1) we generate more and harder negative samples by mixing negative samples, and then sample them by controlling the contrast of anchor sample with the other negative samples. 2) Considering that the negative samples obtained by sampling may have the problem of false negative samples, we further debias the negative samples. Our proposed method improves the classification performance on different image datasets and can be readily applied to existing methods.