Some scholars (e.g. Clarke, 2002) argue that conspiracy theories are ultimately beneficial because they reveal actual anomalies in mainstream explanations and demand greater transparency from governments (see also Leman, 2007). The fact that some conspiracy theories (such as US Department of Defence plans to stimulate acts of terrorism and blame them on Cuba) have turned out to be true certainly bears out this point. Miller (2002) likewise contends that conspiracy theories provide individuals with a public opportunity, otherwise likely denied to them, of addressing the credibility of governments or other socio-political actors. As Fenster (1999, p.109) writes, conspiracies must be recognised as a cultural practice that attempts to map, in narrative form, the trajectories and effects of power. In this view, conspiracy theories may be regarded as the beginnings of social movements that could create positive change and foster solidarity (Sasson, 1995).The same authors, however, are also quick to caution that conspiracy theories remain limited because their critique of power structures is often highly simplistic. In many cases, conspiracy theories succumb to racist or exclusionary narratives, thus losing any positive thrust. Moreover, conspiracy theories typically threaten to unravel and leave unsettled the resolution to the question of power that [they] attempt to address (Fenster, 1999, p.109). For Fenster (1999) and Miller (2002), in particular, conspiracy theories have the potential to create constructive socio-political change, but also the ability to sow discord, violence and public mistrust, while diverting attention from political issues of real significance and undermining democratic debate.Some scholars have also noted the negative practical effects of conspiracy theories on a range of behaviours. Consider, for example, the conspiracy theories held by some that birth control and HIV/AIDS are plots against African Americans (e.g. Bird & Bogart, 2003).Certainly, the history of segregation in the US, the conducting of unethical research with African Americans (such as the Tuskegee syphilis study), and contemporary experiences of racism help explain the existence of such theories. However, adherence to such conspiracy theories has also been associated with less consistent pregnancy prevention and condom use, possibly impacting upon knowledge about HIV/AIDS and AIDS prevention programmes (e.g. Bogart & Thorburn, 2006).Conclusion Documenting the prevalence of conspiracy theories only provides a starting point for tackling their negative effects. Because of their nature, beliefs in conspiracy theories have proven very difficult to repudiate (Keeley, 1999): group members may segregate themselves (informationally, though also, sometimes, physically) and over time become increasingly distrustful of the motives of others. Kramer (1994) called this an example of a sinister attribution error: because in extreme cases they feel under constant scrutiny, individuals may overestimate personalistic motives among others and see purposeful plots where there are in fact benign actions.In such a scenario, what should be the response of scholars and other interested parties? Some authors have recently suggested possible practical means of tackling false and harmful conspiracy theories, such as enlisting independent groups to rebut theories or cognitively infiltrate conspiracist groups (see Sunstein & Vermeule, 2009). The assumption here is that beliefs in conspiracy theories reflect insufficiently critical assimilation of knowledge and that practical steps can