Uncertainty-aware Self-training for Text Classification with Few Labels
This work addresses the annotation bottleneck in NLP for researchers and practitioners by offering an incremental improvement to self-training with uncertainty estimates.
The authors tackled the problem of reducing annotation costs for text classification by proposing an uncertainty-aware self-training method that uses only 20-30 labeled samples per class, achieving within 3% of fully supervised models with an aggregate accuracy of 91% and up to 12% improvement over baselines.
Recent success of large-scale pre-trained language models crucially hinge on fine-tuning them on large amounts of labeled data for the downstream task, that are typically expensive to acquire. In this work, we study self-training as one of the earliest semi-supervised learning approaches to reduce the annotation bottleneck by making use of large-scale unlabeled data for the target task. Standard self-training mechanism randomly samples instances from the unlabeled pool to pseudo-label and augment labeled data. In this work, we propose an approach to improve self-training by incorporating uncertainty estimates of the underlying neural network leveraging recent advances in Bayesian deep learning. Specifically, we propose (i) acquisition functions to select instances from the unlabeled pool leveraging Monte Carlo (MC) Dropout, and (ii) learning mechanism leveraging model confidence for self-training. As an application, we focus on text classification on five benchmark datasets. We show our methods leveraging only 20-30 labeled samples per class for each task for training and for validation can perform within 3% of fully supervised pre-trained language models fine-tuned on thousands of labeled instances with an aggregate accuracy of 91% and improving by upto 12% over baselines.