Résumé : Previous research highlighted that Internet use, in particular online information

retrieval and discussions, can facilitate offline collective actions (Boulianne, 2009).

Recently, however, the Internet also has been criticized for encouraging low-cost and lowrisk

online collective actions—slacktivism—that may have detrimental consequences for

groups that aim to achieve a collective purpose (Gladwell, 2010). More precisely, it is

argued that actions such as “liking” Facebook pages or posting ingroup-endorsing

comments online make users instantly feel good, satisfy their need to act, and derail

participation in offline collective actions (Lee & Hsieh, 2013; Morozov, 2009).

In my thesis, I assessed this postulation as well as the underlying processes and

boundary conditions of the relationship between so-called slacktivist actions and offline

collective actions. After introducing a conceptualization of slacktivism as expressive lowthreshold

online collective actions, I investigated its influence on offline engagement

(Study 1, N = 634; Study 2, N = 76; Study 3, N = 63; Study 4, N = 48). Results indicated that

expressive low-threshold online collective actions reduce the willingness to join offline

collective actions. This effect was mediated by the satisfaction of group-enhancing

motives; members considered the online actions as a substantial contribution to the

group's success. The demobilizing impact of expressive low-threshold online collective

actions was qualified when members took the online actions in the co-presence of the

ingroup, all parties being mutually identifiable (Study 5a, N = 84; Study 5b, N = 99). In this

context, obligatory interdependencies between members were enhanced and fostered a

spill-over from online to offline collective actions (Study 6, N = 62).