Previous research highlighted that Internet use, in particular online information<p>retrieval and discussions, can facilitate offline collective actions (Boulianne, 2009).<p>Recently, however, the Internet also has been criticized for encouraging low-cost and lowrisk<p>online collective actions—slacktivism—that may have detrimental consequences for<p>groups that aim to achieve a collective purpose (Gladwell, 2010). More precisely, it is<p>argued that actions such as “liking” Facebook pages or posting ingroup-endorsing<p>comments online make users instantly feel good, satisfy their need to act, and derail<p>participation in offline collective actions (Lee & Hsieh, 2013; Morozov, 2009).<p>In my thesis, I assessed this postulation as well as the underlying processes and<p>boundary conditions of the relationship between so-called slacktivist actions and offline<p>collective actions. After introducing a conceptualization of slacktivism as expressive lowthreshold<p>online collective actions, I investigated its influence on offline engagement<p>(Study 1, N = 634; Study 2, N = 76; Study 3, N = 63; Study 4, N = 48). Results indicated that<p>expressive low-threshold online collective actions reduce the willingness to join offline<p>collective actions. This effect was mediated by the satisfaction of group-enhancing<p>motives; members considered the online actions as a substantial contribution to the<p>group's success. The demobilizing impact of expressive low-threshold online collective<p>actions was qualified when members took the online actions in the co-presence of the<p>ingroup, all parties being mutually identifiable (Study 5a, N = 84; Study 5b, N = 99). In this<p>context, obligatory interdependencies between members were enhanced and fostered a<p>spill-over from online to offline collective actions (Study 6, N = 62). / Doctorat en Sciences Psychologiques et de l'éducation / info:eu-repo/semantics/nonPublished