Address correspondence to: Nicolás M. Somma, Instituto de Sociología, Facultad de Ciencias Sociales, Pontificia Uni- versidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul (Campus San Joaquín), Casilla 306, Correo 22, Santiago, Chile; e-mail: nsomma@puc.cl. Sociological Perspectives, Vol. 52, Issue 3, pp. 289–308, ISSN 0731-1214, electronic ISSN 1533-8673. © 2009 by Pacific Sociological Association. All rights reserved. Please direct all requests for permission to photo- copy or reproduce article content through the University of California Press’s Rights and Permissions website, at http://www.ucpressjournals.com/reprintinfo.asp. DOI: 10.1525/sop.2009.52.3.289. HOW STRONG ARE STRONG TIES? THE CONDITIONAL EFFECTIVENESS OF STRONG TIES IN PROTEST RECRUITMENT ATTEMPTS NICOLÁS M. SOMMA Pontificia Universidad Católica de Chile and University of Notre Dame ABSTRACT: Why do some individuals accept invitations to participate in protest events while others do not? Using the Citizen Participation Study, the author finds that targets invited by recruiters to whom they are strongly tied are more likely to protest than those invited by weak or absent ties. Such effect, however, is hypothesized to vary across the socioeconomic structure. Although strong ties motivate targets to accept the invitation, only those with sufficient resources could translate motivation into action. Consistent with this hypothesis, while strong ties roughly duplicate the chances of accepting a protest invitation when received by high socioeconomic status (SES) targets, the effectiveness of invitations disappears among low SES targets. This suggests that research about the effects of social networks on protest participation should consider how these networks are embedded in larger socioeconomic structures. Keywords: protest participation; socioeconomic status; strong ties During the last two decades, social movement scholars have explored the sys- tematic differences between participants and nonparticipants in collective protest. They have repeatedly found that features such as high levels of political engage- ment and education (Verba, Schlozman, and Brady 1995), embeddedness in formal associations and informal networks (Diani 2003, 2004; McAdam 1986), a liberal political ideology (Schussman and Soule 2005), and high levels of “biographical availability” (McAdam 1986; Snow, Zurcher, and Ekland-Olson 1980; but see Bey- erlein and Hipp 2006) tend to increase the chances that individuals participate in different kinds of protests and activism (see also Dixon and Roscigno 2003; Fitzgerald and Spohn 2005; Petrie 2004). Although we know much about the correlates of protest, we know less about why some individuals take advantage of protest opportunities—such as being invited to protest—while others do not. Individuals who receive a personal invitation to