On the one hand, some of these rumors may have been kicked off by actual events, in particular the widely publicized New Year’s Eve assaults in the German city of Cologne, wherein hundreds of women reported being robbed or groped by groups of men described by the police chief as appearing “largely from the North African or Arab world.” Among the dozens of suspects identified later, most fell into what Cologne’s prosecutor described as “the general category of refugees,” mainly from North Africa.

At the same time, the pervasive fear of refugee-related crime on display both in German public-opinion polls and Hoaxmap rumors is out of sync with the data so far on the actual relationship between refugees and crime rates in Germany. Recent numbers from Germany’s Federal Criminal Police Agency (BKA) suggest that the influx of refugees into the country this fall had a low impact on crime numbers relative to the natural uptick that would happen with any population increase: Although the number of refugees in the country increased by 440 percent between 2014 and 2015, the number of crimes committed by refugees only increased by 79 percent. (The number of crimes against refugees increased as well.) Furthermore, according to Deutsche Welle’s analysis of the report, the number of offenses increased in the first half of 2015 but “stagnated” in the second half, precisely when most of the refugees were arriving and the rumor mill switched into overdrive. And although sexual offenses account for over 25 percent of the rumors on the Hoaxmap, the BKA data showed that only 1 percent of refugee-related crimes fell into the sexual offense category.

Some of this imbalance between documented crime and crime rumors, sociologists and immigration experts I spoke to suggest, may reflect underlying rules about how rumors spread and the feelings people are primed to have about immigrants. Specifically, rumors are more likely to take off when a factual event similar to the rumor has already occurred, as well as when they tap into an underlying fear: Swan-poaching is never going to rival sexual assault in terms of rumor power.

Gary Alan Fine, a sociology professor at Northwestern University who co-authored a foundational book on the social psychology of rumors as well as a 2010 volume on rumors about terrorism and immigration, pointed to the Cologne assaults as a kind of “template for what people think is plausible.” He noted: “Once you have a plausible story then the criteria for information you need in order to believe [a new story] is much lower, because you would say ‘this is like what happened elsewhere.’” Indeed, almost half of the Hoaxmap’s 76 reports concerning rape and sexual violence occurred in the two months following reports of the Cologne attacks.

And because of how people process information, some stories that appear to be coming out of different cities could even be variations on the same story. “One of the things that is easiest to forget and to change,” said Fine, “is the location of the event.” When a striking story pops up in the United States, for example, “people in Detroit will say ‘oh, that happened in Detroit.’ People in Phoenix will say it happened in Phoenix.” Dates and locations—in this case perhaps even a date as memorable as New Year’s Eve—slip out of focus, because they aren’t central to the story’s social meaning: “What people would remember is if the perpetrator in a story was a Middle Eastern refugee,” Fine said. “Some things get leveled out because we don’t see them as particularly crucial to the story: It happened on Thursday, Tuesday—it doesn’t really matter. Chicago or Detroit, doesn’t really matter. But it matters in terms of the meaning of the story whether it involves Syrian refugee, African American, or Hispanic person. Those kinds of issues become the basis of what makes for a widely spread story.”