  In recent years, social media changed the way individuals participate in
social movements. While activists demonstrate on the street to fight for a
public goal, members of specific movements can also act collective online.
Thus, different aspects might influence the formation of collective identity
and therefore drive collective action on social media. This study combines the
perspectives of social identity- and identity theory in order to examine how
members of an opinion-based group contribute to the collective group/social
identity formation and therefore, to collective action. To this end, we applied
automated text classification techniques to Instagram communication related to
the social movement Fridays for Future. Analysing 1,137 comments showed that
individuals mainly express Group Cohesion and Emotional Attachment rather than
Solidarity by commenting on Instagram. This study further presents a proposed
model of collective group/social identity of collective action. Succeeding
research aims at enhancing the classification and testing the model.
