  Social media platforms have witnessed a substantial increase in social bot
activity, significantly affecting online discourse. Our study explores the
dynamic nature of bot engagement related to Extinction Rebellion climate change
protests from 18 November 2019 to 10 December 2019. We find that bots exert a
greater influence on human behavior than vice versa during heated online
periods. To assess the causal impact of human-bot communication, we compared
communication histories between human users who directly interacted with bots
and matched human users who did not. Our findings demonstrate a consistent
negative impact of bot interactions on subsequent human sentiment, with exposed
users displaying significantly more negative sentiment than their counterparts.
Furthermore, the nature of bot interaction influences human tweeting activity
and the sentiment towards protests. Political astroturfing bots increase
activity, whereas other bots decrease it. Sentiment changes towards protests
depend on the user's original support level, indicating targeted manipulation.
However, bot interactions do not change activists' engagement towards protests.
Despite the seemingly minor impact of individual bot encounters, the cumulative
effect is profound due to the large volume of bot communication. Our findings
underscore the importance of unrestricted access to social media data for
studying the prevalence and influence of social bots, as with new technological
advancements distinguishing between bots and humans becomes nearly impossible.
