Boosting Few-shot Learning by Self-calibration in Feature Space

Few-shot learning aims at adapting models to a novel task with extremely few labeled samples. Fine-tuning the models pre-trained on a base dataset has been recently demonstrated to be an effective approach. However, a dilemma emerges as whether to modify the parameters of the feature extractor. This is because tuning a vast number of parameters based on only a handful of samples tends to induce overfitting, while fixing the parameters leads to inherent bias in the extracted features since the novel classes are unseen for the pre-trained feature extractor. To alleviate this issue, we novelly reformulate fine-tuning as calibrating the biased features of novel samples conditioned on a fixed feature extractor through an auxiliary network. Technically, a self-calibration framework is proposed to construct improved image-level features by progressively performing local alignment based on a self-supervised Transformer. Extensive experiments demonstrate that the proposed method vastly outperforms the state-of-the-art methods.