What can rumors tell you about truth? How do you separate legitimate concerns from prejudice and hysteria? As Europe struggles with its new population of asylum-seekers and the political challenges they present, misinformation has frequently exacerbated an already tense situation. But the bad information itself can also offer useful clues about real worries: a messy map of the daunting political environment European leaders face as they implement a fragile deal to decrease the number of new arrivals.

A case in point is the Hoaxmap project, which two German women created this winter to track and dispel rumors about refugees in their country. Germany received roughly twice as many asylum-seekers as the next most common destination in Europe in 2015, and plenty of false reports accompanied the influx. The map—constructed through a mix of Internet and social-media searches, statements from police officials or involved persons, and more—is hardly a scientific dataset. But the 358 rumors it has gathered, from as far back as 2013, do offer a striking general picture of what people worry about when it comes to refugees. Out of 40 different types of rumors gathered in the Hoaxmap, almost two-thirds pertained to only two types of crimes: some kind of theft or attempted theft, and some type of sexual assault or attempted sexual assault. Stories of parking violations, murder, terrorism, and even swan poaching may pop up occasionally, but simply don’t proliferate in the same way.

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.”

This unconscious information substitution, he cautioned, doesn’t make the stories “hoaxes,” as the name Hoaxmap suggests. “Hoax implies that someone is deliberately spreading false information in order to trick someone for some kind of personal benefit,” he said, “and I don’t think that’s what’s going on.” It’s more likely, he said, that the rumors have their basis in understandable fears. Natalia Banulescu-Bogdan of the Migration Policy Institute echoed the point. “Immigration,” she said, can act as “a proxy for existing insecurities.”

Existing insecurities can be maddeningly difficult to pin down. Justin Berg, who has researched attitudes toward immigration in the United States, noted via email that numerous forms of social priming can contribute to fear of refugees, in addition to straightforward environmental factors like the underlying crime rate and the actual number of new arrivals in any given place. The regions the Hoaxmap reports as sporting the really big numbers of crime rumors are not necessarily the regions with the highest crime rates, nor are they even the regions with the largest numbers of refugees. “[V]arious forms of threat, political ideology, political party, racism, type of immigrant contact, personal education, and media typically play larger roles,” Berg said, “especially when the influx of immigration is relatively quick like it has been in Europe recently.”

In the case of rape rumors specifically, research from the past few decades shows that the type of perceived threat may matter a great deal. “In the United States, among younger women ... rape is feared more than any other crime, including homicide,” Mark Warr, a sociology professor at the University of Texas at Austin who studies patterns in both crime and fear of crime, pointed out via email. Because of that, “even a small increase in apparent risk (like a locally reported rape or rapes) can generate substantial and widespread fear.” Thus the sexual assaults in Cologne might easily have an outsized impact in the rumor world as compared to other reported crimes.

Additionally, the early demographics of refugees arriving in Germany may have had some effect. “By the end of 2015 the arrivals were almost a quarter children, which was extraordinary,” said Banulescu-Bogdan. But earlier, “the flows were predominantly male and came from majority-Muslim countries,” she said, and “this idea that young Muslim men wouldn’t have respect for women became pervasive.” Anglophone Twitter may have mocked the Bavarian Radio’s cartoon guide for refugees, which featured a large orange “X” over a picture of a man groping a woman, but the drawing probably reflected genuine German concerns at the time.

Finally, there’s another possible contributor to the prevalence of rumors about refugees and crime, especially sexual assault: the media’s own apparent reluctance to offer reliable reports of refugee crime. Although police reportedly received 170 complaints regarding women being groped and robbed near the train station in Cologne on New Year’s Eve, it took until January 5 for the story to make national and international headlines, and even longer for arrests to be made. The perceived foot-dragging and bias, according to Banulescu-Bogdan, “really exacerbated people’s fears. They thought ‘everybody’s trying to tell us that we have no reason to be fearful, that our anxieties are illegitimate in some way and look what happened. What else are they covering up?’”

That question goes to the heart of rumor’s power, Fine pointed out. “Whom do you trust?” What one person considers reliable another may find suspect, and just as some of the individuals spreading rumors may have reason to feel vulnerable, “governmental institutions may have a reason for downplaying reports.” When one particular report appears to be downplayed, that adds to skepticism about “establishment” information sources.

Unfortunately for establishment politicians, epistemology rarely wins elections. Fear, on the other hand, has a pretty good track record. As the number of rumors tracked by the activists at Hoaxmap has risen, so have the poll numbers for the right-wing and deeply anti-immigration party Alternative für Deutschland (“Alternative for Germany”). Unless public fear of the ramifications of refugee presence can be allayed, both those numbers—regardless of the success of the EU-Turkey deal slowing the flow of newcomers—may continue to rise.