at the University of North Carolina and a faculty associate at the Berkman Center for Internet & Society, analyzed the capacity of slacktivism to influence collective group action in a variety of different social movements in a segment of the Berkman Luncheon Series. She acknowledges that digital activism is a great enabler of rising social and political movements, and it is an effective means of enabling differential capacity building for protest. A 2015 study describes how slacktivism can contribute to a quicker growth of social protests, by propagation of information through peripheral nodes in social networks. The authors note that although slacktivists are less active than committed minorities, their power lies in their numbers: "their aggregate contribution to the spread of protest messages is comparable in magnitude to that of core participants." However, Tufekci argues that the enhanced ability to rally protest is accompanied by a weakened ability to actually make an impact, as slacktivism can fail to reach the level of protest required in order to bring about change. The Black Lives Matter movement calls for the end of systemic racism. The movement has been inextricably linked with social media since 2014, in particular to Twitter with the hashtags #blacklivesmatter and #BLM. Much of the support and awareness of this movement has been made possible through social media. Studies show that the slacktivism commonly present within the movement has been linked with a positive effect on active participation in it. The fact that participants in this movement were able to contribute from their phones increased awareness and participation of the public, particularly in the United States. The Western-centric nature of the critique of slacktivism discounts the impact it can have in authoritarian or repressive contexts. Journalist Courtney C. Radsch argues that even such low level of engagement was an important form of activism for Arab youth before and during the Arab Spring because it was a form of free speech, and could successfully spark mainstream media coverage, such as when a hashtag becomes "a trending topic [it] helps generate media attention, even as it helps organize information....The power of social media to help shape the international news agenda is one of the ways in which they subvert state authority and power." In addition, studies suggest that "fears of Internet activities supplanting real-life activity are unsubstantiated," in that they do not cause a negative or positive effect on political participation.