Hostility on Twitter in the aftermath of terror attacks

Abstract This study investigates the relationship between major Jihadist terror attacks and manifestations of ethno-religious hostility on social media. Analyzing approximately 4.5 million time-stamped Tweets from 1.2 million users across five European countries, the study focuses on content discussing migration and related topics in the weeks before and after ten significant terror attacks. The findings show a notable and robust increase in hostile Tweets after an attack. An interrupted time series analysis demonstrates a 10% point surge at the time of the attack, followed by a gradual decline. Accordingly, the impact of such attacks on online hostility diminishes approximately seven days after the event. Further analyses reveal that while attacks have the strongest effect on Tweets about Muslims and Islam, the attacks also increase hostility in Tweets about migration in general. We find that the overall attack effect is driven by both intra-user changes in Tweeting and changes in the composition of users posting after an attack. The findings underscore the importance of understanding the interplay between terrorist events and online discourse, shedding light on the dynamics of ethno-religious hostility in the digital realm.