F UTUROS T RABAJOS

Change My View (CMV) is an active subreddit with over 23K subscribers. CMV users provide their beliefs on a subject, are open to different views, and will change their beliefs if convinced by the others’ comments. According to the CMV rules, the original post needs to explain the reasoning behind the view, not just what the view is. Therefore, the posts are required to be at least 500 characters. In addition, CMV rules clearly indicate that the OP “must personally hold the view and be willing to have it changed”.

114 Chapter7. Determinants ofOnlinePersuasion

the OP’s initial view reflected in that post. The poster can then choose to accept the com- ments’ assertion and change his/her belief, ignore them, or engage in a discussion in the form of conversation threads and defer action until he/she is certain about the view. When a comment successfully changes the poster’s view, he/she is required to reply to that com- ment. This reply must include the delta (∆) character that indicates the belief change and should provide an explanation of why and how the comment has changed his/her view. CMV can function as a controlled experimental setting for persuasion studies as it controls for a set of persuasion-related variables such as the belief that is intended to change and the attributes of the user who holds the belief. Specifically, since this platform controls for the

personal relevanceof the belief that has shown to be greatly influential in the persuasion process [48]. Meanwhile, CMV allows variations in another set of variables including the attributes of the users who post the comments and different types of language and writing styles used in the comments. CMV is heavily moderated, controlling for any posts or com- ments that are not following the rules. The CMV’s delta mechanisms along with its strict rules provide a unique and a valuable dataset for studying online persuasion.

Figure 7.1 shows an example post submitted to CMV, along with three selected com- ments that are provided to change the original view. The top section of the first block shows the title of the post along with the time of submission and the OP’s username. The bottom part is the OP’s view and reasoning. The next three blocks with a solid border are comments provided to change the view. As can be seen, each comment is associated with the commenter’s username and overall delta score (i.e., the number of times this user has received a delta so far), and the comment score (i.e., the number of upvotes deducted by the number of downvotes the comment has received so far), and the timestamp of the comment submission. Finally, the block with the dotted border is a reply to the first comment, with the delta (∆) character and the rationale for giving the delta (∆) to the comment. It should be noted that the metadata presented in the example and their placement is the same as the actual CMV interface.

As mentioned, CMV comments can occur in the form of threaded discussions, where CMV users can reply to other comments and build a discussion tree. A delta can be awarded to comments at different levels of the tree. In our study, however, we have only focused on the top-level comments, which are the direct replies to the post and so serve as the root comment in each thread. By focusing only on the root comments, we can ensure that the persuasive aspects lie within the comment itself but not the conversational context that takes place through a comment thread. Given that we are focused on the root comments, from now on, whenever we say comment, we refer to a root comment. In addition, by persuasive or successful comments we refer to the comments that have won a delta, whereas the non-

7.3. RedditDataset 115

Figure 7.1: Example of a CMV post, along with the comments provided to change the view.

116 Chapter7. Determinants ofOnlinePersuasion

Entity Total Unique Users post 4,853 3,592

root comment 58,242 13,920 persuasive root comment (∆) 1,771 1,019 persuaded post (∆) 1,272 1,108

Table 7.1: Data statistics persuasive ones are the ones that have not received a delta.

From February 2015 to January 2016, we collected posts and their comments from CMV. In Reddit, when a user or a textual content of a comment or post is no longer avail- able, the corresponding data field is assigned the value of[deleted]or[removed]. We report the data statistics after the cleaning of such data points. Also, only a small portion (less than 5%) of the attempts to persuade through root comments are perceived persuasive and thus are given a delta. To reliably compare the persuasive and non-persuasive comments, we need to control a set of variables. One of the most important factors to take care of is the post that the comments are provided for, since the topic of the post and the OP’s characteristics may affect the persuasion process. Therefore, we only focused on the posts that are associated with at least one successful comment. In addition, for the sake of com- parison, we filtered this set to only include the posts that have at least 5 comments. This filtering process resulted in 1,249 posts and 18,534 comments associated with these posts, among which 1690 comments have received a delta. The statistics of our finalized data set is summarized in Table 7.1.