Empirical Methodology for Crowdsourcing Ground Truth

The process of gathering ground truth data through human annotation is a major bottleneck in the use of information extraction methods for populating the Semantic Web. Crowdsourcing-based approaches are gaining popularity in the attempt to solve the issues related to volume of data and lack of annotators. Typically these practices use inter-annotator agreement as a measure of quality. However, in many domains, such as event detection, there is ambiguity in the data, as well as a multitude of perspectives of the information examples. We present an empirically derived methodology for efficiently gathering of ground truth data in a diverse set of use cases covering a variety of domains and annotation tasks. Central to our approach is the use of CrowdTruth metrics that capture inter-annotator disagreement. We show that measuring disagreement is essential for acquiring a high quality ground truth. We achieve this by comparing the quality of the data aggregated with CrowdTruth metrics with majority vote, over a set of diverse crowdsourcing tasks: Medical Relation Extraction, Twitter Event Identification, News Event Extraction and Sound Interpretation. We also show that an increased number of crowd workers leads to growth and stabilization in the quality of annotations, going against the usual practice of employing a small number of annotators.Comment: in publication at the Semantic Web Journa

The 'Problem' of Human Label Variation: On Ground Truth in Data, Modeling and Evaluation

Human variation in labeling is often considered noise. Annotation projects for machine learning (ML) aim at minimizing human label variation, with the assumption to maximize data quality and in turn optimize and maximize machine learning metrics. However, this conventional practice assumes that there exists a ground truth, and neglects that there exists genuine human variation in labeling due to disagreement, subjectivity in annotation or multiple plausible answers. In this position paper, we argue that this big open problem of human label variation persists and critically needs more attention to move our field forward. This is because human label variation impacts all stages of the ML pipeline: data, modeling and evaluation. However, few works consider all of these dimensions jointly; and existing research is fragmented. We reconcile different previously proposed notions of human label variation, provide a repository of publicly-available datasets with un-aggregated labels, depict approaches proposed so far, identify gaps and suggest ways forward. As datasets are becoming increasingly available, we hope that this synthesized view on the 'problem' will lead to an open discussion on possible strategies to devise fundamentally new directions.Comment: EMNLP 202

Making the Most of Crowd Information: Learning and Evaluation in AI tasks with Disagreements.

PhD ThesesThere is plenty of evidence that humans disagree on the interpretation of many tasks in Natural Language Processing (nlp) and Computer Vision (cv), from objective tasks rooted in linguistics such as part-of-speech tagging to more subjective (observerdependent) tasks such as classifying an image or deciding whether a proposition follows from a certain premise. While most learning in Artificial Intelligence (ai) still relies on the assumption that a single interpretation, captured by the gold label, exists for each item, a growing research body in recent years has focused on learning methods that do not rely on this assumption. Rather, they aim to learn ranges of truth amidst disagreement. This PhD research makes a contribution to this field of study. Firstly, we analytically review the evidence for disagreement on nlp and cv tasks, focusing on tasks where substantial datasets with such information have been created. As part of this review, we also discuss the most popular approaches to training models from datasets containing multiple judgments and group these methods together according to their handling of disagreement. Secondly, we make three proposals for learning with disagreement; soft-loss, multi-task learning from gold and crowds, and automatic temperature-scaled soft-loss. Thirdly, we address one gap in this field of study – the prevalence of hard metrics for model evaluation even when the gold assumption is shown to be an idealization – by proposing several previously existing metrics and novel soft metrics that do not make this assumption and analyzing the merits and assumptions of all the metrics, hard and soft. Finally, we carry out a systematic investigation of the key proposals in learning with disagreement by training them across several tasks, considering several ways to evaluate the resulting models and assessing the conditions under which each approach is effective. This is a key contribution of this research as research in learning with disagreement do not often test proposals across tasks, compare proposals with a variety of approaches, or evaluate using both soft metrics and hard metrics. The results obtained suggest, first of all, that it is essential to reach a consensus on how to evaluate models. This is because the relative performance of the various training methods is critically affected by the chosen form of evaluation. Secondly, we observed a strong dataset effect. With substantial datasets, providing many judgments by high-quality coders for each item, training directly with soft labels achieved better results than training from aggregated or even gold labels. This result holds for both hard and soft evaluation. But when the above conditions do not hold, leveraging both gold and soft labels generally achieved the best results in the hard evaluation. All datasets and models employed in this paper are freely available as supplementary materials

A Conceptual Probabilistic Framework for Annotation Aggregation of Citizen Science Data

Over the last decade, hundreds of thousands of volunteers have contributed to science by collecting or analyzing data. This public participation in science, also known as citizen science, has contributed to significant discoveries and led to publications in major scientific journals. However, little attention has been paid to data quality issues. In this work we argue that being able to determine the accuracy of data obtained by crowdsourcing is a fundamental question and we point out that, for many real-life scenarios, mathematical tools and processes for the evaluation of data quality are missing. We propose a probabilistic methodology for the evaluation of the accuracy of labeling data obtained by crowdsourcing in citizen science. The methodology builds on an abstract probabilistic graphical model formalism, which is shown to generalize some already existing label aggregation models. We show how to make practical use of the methodology through a comparison of data obtained from different citizen science communities analyzing the earthquake that took place in Albania in 2019

Incorporating Clicks, Attention and Satisfaction into a Search Engine Result Page Evaluation Model

Modern search engine result pages often provide immediate value to users and organize information in such a way that it is easy to navigate. The core ranking function contributes to this and so do result snippets, smart organization of result blocks and extensive use of one-box answers or side panels. While they are useful to the user and help search engines to stand out, such features present two big challenges for evaluation. First, the presence of such elements on a search engine result page (SERP) may lead to the absence of clicks, which is, however, not related to dissatisfaction, so-called "good abandonments." Second, the non-linear layout and visual difference of SERP items may lead to non-trivial patterns of user attention, which is not captured by existing evaluation metrics. In this paper we propose a model of user behavior on a SERP that jointly captures click behavior, user attention and satisfaction, the CAS model, and demonstrate that it gives more accurate predictions of user actions and self-reported satisfaction than existing models based on clicks alone. We use the CAS model to build a novel evaluation metric that can be applied to non-linear SERP layouts and that can account for the utility that users obtain directly on a SERP. We demonstrate that this metric shows better agreement with user-reported satisfaction than conventional evaluation metrics.Comment: CIKM2016, Proceedings of the 25th ACM International Conference on Information and Knowledge Management. 201