Interpreting Dense Retrieval as Mixture of Topics
This provides insights into why dense retrieval works, which is incremental for researchers in information retrieval.
The paper tackles the problem of interpreting dense retrieval models by analyzing their mechanisms, finding that these models learn representations as a mixture of high-level topics through qualitative and quantitative experiments on public test collections.
Dense Retrieval (DR) reaches state-of-the-art results in first-stage retrieval, but little is known about the mechanisms that contribute to its success. Therefore, in this work, we conduct an interpretation study of recently proposed DR models. Specifically, we first discretize the embeddings output by the document and query encoders. Based on the discrete representations, we analyze the attribution of input tokens. Both qualitative and quantitative experiments are carried out on public test collections. Results suggest that DR models pay attention to different aspects of input and extract various high-level topic representations. Therefore, we can regard the representations learned by DR models as a mixture of high-level topics.