This study aimed to: 1) evaluate Twitter as a viable tool for promoting collaborative argumentation; 2) determine if scripting through sentence openers promotes a greater number of arguments within an online discussion; and 3) compare Twitter to Facebook as viable tools for promoting collaborative argumentation. Participants were 27 undergraduate students enrolled in an online introductory Educational Psychology course. A quasi-experimental, sequential explanatory mixed methods research design was employed. Data analysis focused on the difference in the number of argument components generated by participants between the two social media platforms, Twitter and Facebook. In addition, the impact of participants' use of sentence openers on the amount of argument components was also examined. Facebook was found to be a more viable tool for promoting online collaborative argumentation, and specific affordances of Facebook were identified.