On the role of human and machine metadata in relevance judgment tasks

In order to evaluate the effectiveness of Information Retrieval (IR) systems it is key to collect relevance judgments from human assessors. Crowdsourcing has successfully been used as a method to scale-up the collection of manual relevance judgments, and previous research has investigated the impact of different judgment task design elements (e.g., highlighting query keywords in the document) on judgment quality and efficiency. In this work we investigate the positive and negative impacts of presenting crowd human assessors with more than just the topic and the document to be judged. We deploy different variants of crowdsourced relevance judgment tasks following a between-subjects design in which we present different types of metadata to the human assessor. Specifically, we investigate the effect of human metadata (e.g., what other human assessors think of the current document, as in which relevance level has already been selected by the majority crowd workers), machine metadata (e.g., how IR systems scored this document such as its average position in ranked lists, statistics about the document such as term frequencies). We look at the impact of metadata on judgment quality (i.e., the level of agreement with trained assessors) and cost (i.e., the time it takes for workers to complete the judgments) as well as at how metadata quality positively or negatively impact the collected judgments.