Meta-Embedding as Auxiliary Task Regularization
This work addresses the problem of enhancing word embeddings for NLP researchers and practitioners, but it is incremental as it builds on existing ensemble and self-supervised methods by incorporating labeled data as regularization.
The paper tackled the problem of improving word embeddings by using an auxiliary task to reconstruct an ensemble of embeddings, which regularizes a main task and shares a meta-embedding layer. The result showed performance improvements across all word similarity datasets with a mean increase of 11.33 in Spearman correlation, and enhancements in downstream tasks like sequence tagging and sentence classification.
Word embeddings have been shown to benefit from ensambling several word embedding sources, often carried out using straightforward mathematical operations over the set of word vectors. More recently, self-supervised learning has been used to find a lower-dimensional representation, similar in size to the individual word embeddings within the ensemble. However, these methods do not use the available manually labeled datasets that are often used solely for the purpose of evaluation. We propose to reconstruct an ensemble of word embeddings as an auxiliary task that regularises a main task while both tasks share the learned meta-embedding layer. We carry out intrinsic evaluation (6 word similarity datasets and 3 analogy datasets) and extrinsic evaluation (4 downstream tasks). For intrinsic task evaluation, supervision comes from various labeled word similarity datasets. Our experimental results show that the performance is improved for all word similarity datasets when compared to self-supervised learning methods with a mean increase of $11.33$ in Spearman correlation. Specifically, the proposed method shows the best performance in 4 out of 6 of word similarity datasets when using a cosine reconstruction loss and Brier's word similarity loss. Moreover, improvements are also made when performing word meta-embedding reconstruction in sequence tagging and sentence meta-embedding for sentence classification.