Exploring Atypical Online Coincidental Behavior on PTT

This study focuses on atypical coincidental behavior on the Taiwan social media, PTT1, to discover attempts to manipulate public opinion during the outbreak of the COVID-19 in Taiwan from May through August 2021. The research team aims to identify atypical coincidental behaviors to uncover suspicious collaborative efforts which attempt to manipulate public opinions, together with developing AI tools to analyze the information comprehensively and efficiently over the outbreak period and assists researchers by saving human labor and time.

Since its launch in 1995, PTT has become one of the most used Chinese-language online services. In Taiwan, many users make it a habit to post news and information from various sources, which leads to a diverse spectrum of discussions, and often for many, the discussion board becomes the first stop of the news outlet. Almost all the information related to Taiwan can be discovered on PTT. The information on PTT is discussed by users with their opinions and ideas.

Such discussions are often later presented in news media for larger public consumption. This effect not only amplifies these ideas for a wider audience, but it also affects businesses and governmental institutions during their decision-making process when they need to adhere to public opinions. For example, when whistle-blower Dr. Wenliang Li of China first broke evidence in Chinese media of human-to-human transmission of COVID-19, a Taiwanese physician began sharing the information on PTT. Because of these discussions, authorities at the Taiwan Centers for Disease Control were alerted and began to take action much earlier than other countries. In this way, one could compare PTT to a speech stand in the center of the town square, upon which users can take space to give public addresses where the majority of the townsfolks are the audience. The more time someone spends on the speaker stand, the greater potential influence they will have on the town. Users who have the power to influence discussions could be likened to a bullying majority dominating the use of the speaker stands for their own ends.

Since 2018, Taiwan media and academia have been observed the potential of cyber armies conducting strategic information operations through social networks such as PTT, Line, and Facebook. A Pilot Study on PTT in the Context of Influence Operations introduces the interface, functions, and terminology of PTT. Other studies identified groups of cyber armies on the Gossiping Board of PTT. Compared to previous papers, this research contains not only case studies but also a data-driven and evidence-based approach, comprehensively quantifies “atypical coincidental behavior” and summarizes the differences between user groups.

The research team grouped users by the phi-coefficient score to measure coincidental behavior in many aspects, including shared IP addresses, time pattern of activity, narratives, emotion, and incitement of comments. Furthermore, the study compared several metrics of behavior among user groups in various events2 to discover the evidence of information manipulation and observed the correlation between ideological slogans used and groups of users. By observing the opinion manipulation on social media, users may be able to more readily distinguish atypical coincidental behavior and therefore decrease their chances of being manipulated. Through exposing more context behind user content, this research hopes to decrease the negative impact of atypical coincidental behavior on public opinion.

Furthermore, the researchers compared the behavior of coincidental users. Between the shared IP addresses, active times, narratives, etc., the researchers conclude that these patterns reflect more than just random chance. The evidence shows those coincidental users were engaged in various forms of intentional, collaborative effort in their posts, comments, and other behaviors. Although one cannot claim for certain that the intent of these users is to manipulate public opinion, the researchers cannot conclude any other plausible explanation to justify such behavior because it is so different from typical general users.

The following collaborative behaviors were observed during this time period:

  1. Users in each coincidental user groups were active during similar times
  2. Coincidental users were more likely to participate in events with more comments, and in events with higher incite scores
  3. Coincidental users showed much higher rates of manipulative patterns
  4. Each coincidental user group demonstrated different preferences in their patterns of behavior
  5. Some coincidental user groups favored just one negative/manipulative slogan, while others used more than one, or none at all.
  6. Different coincidental user groups favored different specific narratives and word choices.

In summary, the researchers want to emphasize that behavior indicative of the intent to manipulate opinions on social media platforms appears to be very active. In the time period selected for this study, there were 880 atypical events out of 1,985 targeted events. This means that there were collaborative users demonstrating intentionally manipulative behaviors in almost half of all targeted events. This report also showed that manipulation could and does happen on a variety of topics, including sporting, business, entertainment, politics, etc. The research team believes that more work should be done to study and catalog atypical, manipulative behaviors on social media across a variety of platforms. We believe that users of social media platforms should be made aware of collaborative, manipulative behavior in order to know when others may be attempting to influence public opinion.

to download the complete version of the research paper, please submit the request form at the end of this blog


This study focused on atypical coincidental behavior attempting to uncover the types of events that were manipulated via social media and the ways in which they were manipulated. To do so, the important events that happened during the Taiwanese outbreak of the COVID-19 pandemic, as well as the users with coincidental behavior, had to be identified to study the interactions between the events and the coincidental users.

Figure 1 presents an overview of the methodology framework. With the framework provided, all the data posted on the PTT Gossiping Board from May 1, 2021, to August 31, 2021, including 130,099 users and 8,413,675 comments on 293,370 posts, were analyzed to detect events and group users. Additionally, through the comment content analysis, features were extracted for the study of the interactions between the events and the coincidental users. With the results obtained from event user analysis and comment content analysis, coincidental users were first analyzed, then coincidental groups were analyzed.

GitHub: https://github.com/ailabstw/opinion-analysis


1 PTT is the largest local forum in Taiwan.

2 This research defines an ”event” as the sum total of collected news articles on a topic, combined with all social media reactions to it, on given platforms. For more details about how the data was clustered, please download the complete essay and refer to Chapter II Methodology.