Paradoxically, the presence of official personnel—whether police officers, rescue workers, scientific investigators, or government officials—often worsens the epidemic, for it reinforces the belief that something serious is going on and that the situation is potentially dangerous. When these same officials attempt to provide reassurance that the situation is safe and that no cause was found, it typically generates deep suspicions among the emotionally charged populace that a cover-up is under way, especially because the official response was previously so substantial. Paranoia can spread too, undermining the very authority that is needed to bring an end to such an episode.
The recommended treatment for MPI outbreaks focuses on social networks and recognizes that social ties are the medium for spread. The psychological guidelines for emergency workers include “providing reassurance…using a calm and authoritative approach” and “separating those who are ill from those who are not.”20 As one expert put it, “You can only stop these things by being honest…. I could get caught up in this kind of thing too, as a parent or just a person. We all could. It’s a very powerful thing, and it needs to be respected and understood. And health officials shouldn’t be so scared to call a spade a spade.”21
It’s often difficult to establish why exactly these epidemics start. Just as an unfamiliar noise can trigger a cattle herd to start running, many triggers can cause emotional stampedes. However, it is usually fairly simple to identify the initial cases. For example, in the African laughing epidemic, even though the investigators could not explain why it started, they easily located the first girls to have symptoms.
It only took a few people to start La Ola in the stadium in Mexico City or to get passersby to stop and look up at a window in New York City, and the same is true of MPI outbreaks. When a small group of people begin acting in concert or experiencing similar, visible symptoms, the epidemic can spread along social-network ties via emotional contagion, and large groups can very quickly become emotionally synchronized.
The present obsession with nut allergies in the United States may be a case in point. The number of schools declaring themselves to be entirely “nut free” is by all accounts rising. Nuts and staples like peanut butter are prohibited from campus, and so are homemade baked goods and any foods without detailed ingredient labels. School entrances have signs admonishing visitors to wash their hands before entering to safeguard students from possible contamination.
Approximately 3.3 million Americans are allergic to nuts, and even more, 6.9 million, are allergic to seafood. However, all told, serious allergic reactions to foods cause just two thousand hospitalizations per year (out of more than thirty million hospitalizations nationwide). And, at most, only 150 people (both children and adults) die each year from food allergies. Compare that to the fifty people who die each year from bee stings, the hundred who die from lightning strikes, and the forty-five thousand who die from motor vehicle accidents. Or compare that to the ten thousand children who are hospitalized each year for traumatic brain injuries acquired during sports, or the two thousand who drown, or the roughly thirteen hundred who die from gun accidents. Yet there are no calls to end athletics. There are likely thousands of parents who rid their cupboards of peanut butter but not guns. And more children assuredly die walking or being driven to school each year than die of nut allergies.
The question is not whether nut allergies exist, or whether they can occasionally be serious, or whether reasonable accommodations should be made for the few children who have documented serious allergies. The question is, what accounts for society’s extreme response to nut allergies? Not surprisingly, the response bears many of the hallmarks of MPI. A few people have clinically documented concerns, but others who do not then copy the behaviors of those who do. Anxiety spreads from person to person to person, and a sense of proportion and the ability to be reassured are lost.
Well-intentioned efforts to reduce nut exposure actually fan the flames since they indicate to parents that nuts are a clear and present danger. This encourages more parents to worry, which fuels the epidemic. It also encourages more parents to have their kids tested, thus detecting mild and meaningless allergies to nuts. And, finally, this encourages still more avoidance of nuts, which may actually lead to a rise in true nut allergies because lack of exposure to allergens early in life is thought to contribute to the onset of allergies later.22
MPI is a pathological phenomenon, but it takes advantage of a nonpathological process that is fundamental in humans, namely, the tendency to mimic the emotional state of others. Real laughter also can be contagious and so can real happiness. But comparing epidemic hysteria to these more normal processes is like comparing the stampede of a herd to its more usual and orderly migration.
Tracking the Spread of Emotions
Measuring the subjective experience of emotions (as compared with their visible, biological, or neurological manifestations) requires asking people how they are feeling. One of the more systematic ways of doing this is known as the experience-sampling method. This method uses a series of alerts (such as signals sent to a beeper or cell phone) at unexpected times to prompt subjects to document their feelings, thoughts, and actions while they are experiencing them.23 The result is a thorough picture of the ups and downs of subjects’ daily emotional lives.
One of the advantages of this method is that it allows groups of interacting people to be evaluated simultaneously in real time. For example, one team of investigators, interested in the spread of emotions within families, outfitted fifty-five families (consisting of a mother, father, and one adolescent) with beepers for one week. The participants were beeped roughly every 90 to 120 minutes between 7:30 a.m. and 9:30 p.m., and a total of 7,100 time points were observed in these 165 individuals. Various emotional states were measured, such as whether the subjects were happy or unhappy. Although the investigators could not rule out the possibility that the entire family was simultaneously exposed to one thing that made them all sad or happy at once (a confounding effect that we will discuss in greater detail in chapter 4), they did try to tease out how emotions spread within these families.
The strongest path was from daughters to both parents, while, conversely, the parents’ emotional state appeared to have no effect on their daughters. Fathers’ emotions affected their wives and their sons but not their daughters. This appeared to be especially true when fathers returned from work: when dad came home in a lousy mood, he soon made the whole household miserable.24
A similar method has been used to examine the transmission of emotions among teams of nurses, athletes, and even accountants.25 In such professional settings, a key question was whether one fired-up team member could improve the mood and thus the performance of his teammates. Not surprisingly, positive mood is associated with a range of team-performance-enhancing changes, including greater altruistic behavior, increased creativity, and more efficient decision making. A nice demonstration involved outfitting thirty-three professional male cricket players with pocket computers that recorded their moods four times a day during a match (which can have the insane duration of five days). There was a strong association between a player’s own happiness and the happiness of his teammates, independent of the state of the game; further, when a player’s teammates were happier, the team’s performance improved.
The Spread of Happiness
Despite the biological