Research suggests that a vicious cycle of bigotry and isolation could reduce assimilation and increase bigotry towards immigrants in the long-term. For instance, University of California, San Diego political scientist Claire Adida, Stanford University political scientist David Laitin and Sorbonne University economist Marie-Anne Valfort argue "fear-based policies that target groups of people according to their religion or region of origin are counter-productive. Our own research, which explains the failed integration of Muslim immigrants in France, suggests that such policies can feed into a vicious cycle that damages national security. French Islamophobia—a response to cultural difference—has encouraged Muslim immigrants to withdraw from French society, which then feeds back into French Islamophobia, thus further exacerbating Muslims' alienation, and so on. Indeed, the failure of French security in 2015 was likely due to police tactics that intimidated rather than welcomed the children of immigrants—an approach that makes it hard to obtain crucial information from community members about potential threats."