Overview of the CLEF--2021 CheckThat! Lab on Detecting Check-Worthy Claims, Previously Fact-Checked Claims, and Fake News

TL;DR

The CLEF-2021 CheckThat! Lab evaluated multilingual systems on detecting check-worthy claims, verifying claims, and assessing news veracity across five languages, with high participation and diverse tasks.

Contribution

This paper presents the design, tasks, and participation details of the fourth CheckThat! Lab, focusing on multilingual fact-checking and fake news detection in a competitive evaluation setting.

Findings

High team participation with 132 registered teams.

Multiple tasks covering different aspects of fact-checking.

Evaluation results highlight the current state of multilingual fake news detection.

Abstract

We describe the fourth edition of the CheckThat! Lab, part of the 2021 Conference and Labs of the Evaluation Forum (CLEF). The lab evaluates technology supporting tasks related to factuality, and covers Arabic, Bulgarian, English, Spanish, and Turkish. Task 1 asks to predict which posts in a Twitter stream are worth fact-checking, focusing on COVID-19 and politics (in all five languages). Task 2 asks to determine whether a claim in a tweet can be verified using a set of previously fact-checked claims (in Arabic and English). Task 3 asks to predict the veracity of a news article and its topical domain (in English). The evaluation is based on mean average precision or precision at rank k for the ranking tasks, and macro-F1 for the classification tasks. This was the most popular CLEF-2021 lab in terms of team registrations: 132 teams. Nearly one-third of them participated: 15, 5, and 25 teams submitted official runs for tasks 1, 2, and 3, respectively.