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Boston Lockdown–Fear, Uncertainty and Bias

The views expressed are those of the author and are not necessarily those of Scientific American.

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Prudential building on 4th of July

Prudential building on 4th of July

Like many other Bostonians on Friday, April 19th, I was stuck inside all day, obsessively following twitter, cable news and police scanners. As I sat voluntarily confined to my home, several miles away from any apparent danger, I didn’t see anything wrong with what was being asked of me and my city. A city wide-lockdown was clearly extraordinary, but we were living through extraordinary times; it seemed justified.

But was it?

No one denies the tragedy of the Boston Marathon bombing, which killed three people and severely injured hundreds of others, but there are many other tragedies that go seemingly unnoticed. In the first three months of 2013, there were 10 homicides in Boston, and in 2012, there were 51 homicides, including a triple homicide on August 12th. As far as I could determine, there hasn’t been an arrest in that latter case – why no citywide manhunt to find those three victims’ killer? What is it that makes three dead and 282 wounded more emotionally salient than the 2.3 million people killed or injured in car accidents every year (that’s over six thousand per day)? Why does it make sense to shut down all the economic activity of a major American city to catch two murderers, but politicians are ridiculed for attempting to cut back on the tens of thousands of deaths attributable to diabetes each year?

The fact is, our ape brains are profoundly bad at assessing risk in the modern world. Evolved for anticipating danger on the savannahs of Africa, in relatively small groups where the spectrum of potential dangers are relatively small, our brains use a number of assumptions or “heuristics” in order to understand the world – and these assumptions are often wrong. Research over the past several decades has begun to shine a light on why I’m more afraid of terrorists than of car crashes, even though the latter is far more likely to kill me.

The Availability Heuristic

Are there more words in the English language that begin with the letter “R,” or that have “R” as the third letter? If you’re like most people, it’s much easier to call to mind words that begin with “R,” and you therefore assume that such words are more numerous. In fact, there are three times as many words that have “R” in the third position.

In general, it makes sense to think that the easier it is to recall an example of a thing, the more common that thing is. But ease of recall can be easily skewed by a number of factors. Try this: try to recall five terrorist attacks. Right off the top of my head I can recall 9/11, 7/7, Oklahoma city, Mumbai and Benghazi – personally, that took me about ten seconds. You might have a different list, but I’m willing to bet it was pretty easy. Now, try to recall five fatal car accidents. I thought of Princess Diana, and a friend from highschool that was killed by a drunk driver. That’s it. I might be able to rack my brain for some other examples, but those are the only ones that spring immediately to mind. In terms of people killed, it’s terrorists: thousands, car accidents: 3. Based on ease of recall, I might be forgiven for thinking that terrorism is a far greater threat than car accidents.

In reality, less than ten thousand people have died in the US as the result of terrorist attacks in the last 20 years, while at least that many die behind the wheel every year.

The Illusion of Control and Illusory Superiority Bias

Rational people might scoff at the sports fan that wears his lucky hat to the game (or Robert De Niro’s character in Silver Linings Playbook), but we all suffer from the erroneous belief that our actions have more impact than they actually do. In a 1980 study, subjects were given a button to press, and shown lights labeled “Score” or “No Score” that would flash at pre-set intervals. Despite the fact that there was no connection between pressing the button and flashing lights, subjects still believed they had some measure of control.

We also believe we are better than other people. When asked, clear majorities of people believe themselves to be better than average in terms of IQ, memory, and job performance. In one of the earliest studies of this sort, 25% of respondents believed themselves to be in the top 1% in terms of ability to get along well with others. Mathematically, it’s clear that these people can’t all be correct.

Because of our illusory superiority, we feel safer when we are in control of a situation, and our illusions of control lead us to believe that we are more in control of some situations than we actually are. Respondents consistently rate the likelihood of a driving accident as significantly lower when they are driving than when someone else is driving. This is also why people tend to be more afraid of commercial flying than of driving – we have no control over the what goes on in the cockpit. Terrorism is terrifying precisely because it is out of our control.

Zero-Risk Bias

The federal budget for the Transportation Security Administration (the folks that check your bags at airports) in 2012 was $7.8 billion. By contrast, the Centers for Disease Control and Prevention (CDC) received just $6.1 billion. The CDC’s mandate covers just about every risk to human health, including infectious disease, non-communicable diseases like cancer, and even accidental death.

Imagine that if you doubled the CDC’s budget, it could reduce the incidence of infectious and non-communicable diseases by 2%, but that all of the money would come from the TSA, leaving it with only $1.7 billion to protect airlines and railways. Now imagine that the TSA claimed that this reduction would allow a 9/11-scale terrorist attack to occur every year – would you take that deal? I certainly wouldn’t and I’d venture to guess that any politician proposing such a scheme would be run out of office. But if you go by the numbers, the CDC would be a better bet.

The top five causes of death in the US are (in order) heart disease, cancer, respiratory diseases (like pneumonia), stroke and accidents. The infectious and non-communicable diseases on this list alone account for about 1.5 million deaths in 2010, meaning a 2% reduction would save thirty thousand people per year, almost ten times the number that would die from terrorism in this scenario. Knowing this, would you be willing to take the deal now?

The reason that the math seems so counter-intuitive is something called the zero-risk bias – we are far more inclined to reduce unlikely threats to zero than to make small reductions in much more probable threats, even if the latter have a much greater overall benefit.

Just World Hypothesis

Perhaps the most pernicious bias is our brain’s tendency to interpret the world in ways that suggest that good people are rewarded and bad people are punished. This bias is responsible for the assumption that if someone is rich, they must have worked hard to be successful, and if someone is poor, they must be lazy. It also allows people to ignore or downplay many risks. If someone is in a car wreck for instance, they must have been a bad driver. Yes, a lot of people die from gun violence every year, but it’s only the poor (lazy) people that joined gangs.

Events like terrorist attacks are all the more frightening because, we can’t rationalize them away as

Safety, Security and Fear

Events like terrorist attacks are all the more frightening because we can’t rationalize them away as just consequences of the victim’s actions. What does all of this mean? Was shutting down Boston the right thing to do? None of the people I’ve talked to that live here were against the idea, and most of the city diligently followed orders. But that one day could cost hundreds of millions of dollars in lost productivity, not to mention the cost in overtime pay for the police, lost revenue for the public transit system etc. We should ask ourselves if it was worth it.

In hindsight, it’s unlikely that Dzokhar Tsarnaev was much of a threat in his condition, but knowing what we knew early on that Friday morning, was the decision the right one? I’m not in a position to evaluate the risk, let alone measure the cost of a life or lives that might have been lost. I’m grateful to the public officials and law enforcement agencies that acted heroically in the face of a profoundly difficult situation. But knowing what we know about how fear can negatively influence our decisions, it’s worth understanding where that fear comes from. And when we’re making decision in the midst of that fear, understanding might help us confront our biases, and make decisions based on reality, rather than our imperfect perception of it.

Images: Image 1 by author, Image 2 from CBS News, Image 3, by Deviant Art user ADDattack with permission, Image 4 by Flickr user  jurvetson.

Kevin Bonham About the Author: Kevin Bonham is a Curriculum Fellow in the Microbiology and Immunobiology department at Harvard Medical school. He received his PhD from Harvard, where he studied how the cells of the immune system detect the presence of infectious microbes. Find him on Google+, Reddit. Follow on Twitter @Kevbonham.

The views expressed are those of the author and are not necessarily those of Scientific American.

Comments 16 Comments

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  1. 1. curiouswavefunction 2:05 pm 04/29/2013

    Nice post. I was reading Steven Pinker’s latest book yesterday and he made exactly the same point. He pointed to a 1984 paper by Kahneman and others which described how people react disproportionately to risk if that risk is perceived to arise from unfamiliar and alien sources like terrorism rather than familiar ones like car accidents. As both Pinker and you point out, in reality the deaths caused by terrorism are a fraction of the deaths from any other source, including for instance falls in bathrooms.

    In fact, considering their limited resources and the limited destruction that they can cause, this disproportionate response that induces a constant state of fear and leads to significant losses related to the economy and to personal freedom is exactly the kind of response the terrorists want. Their whole premise is based on the response to their efforts rather than the efforts themselves. The only way to stop the terrorists from winning then is to mourn the dead and injured and then go about our normal lives with resolve and nonchalance. The only way terrorists can be dissuaded is if they realize that their actions are not making a measurable difference in our lives. Fortunately, apart from the lockdown, there have been promising signs of this in Boston (I live in Boston too).

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  2. 2. paulus 4:36 pm 04/29/2013

    First of all, I deny that what happened in Boston was a tragedy in any way. It was terrible, it was a horror, and the deaths of innocents is always tragic–but never a tragedy. It is important that we understand the words we are using because it is these words which underlie the bias in judgment we assume when reacting to the word ‘tragedy’.

    But since ‘tragedy’ evokes a feeling of complete loss, did its prominent use have a psychological impact in decisions authorities made to stop lawful citizens from engaging in their everyday activities?

    I believe it did, and continues to have a bearing on the question of reaction to the bombs in Boston.

    Every day we read, hear, or see evidence of bombs being used around the world. Yet when there is a bomb used to maim and kill in Boston, we are informed an act of terror has been committed.

    We must be careful how we define an act of violence, and if we truly wish to disempower those we refer to as terrorists, it may be more effective to use the language of homicide detectives, and call them mass killers. A terrorist is only that if the population is terrorized; and a population that is not fearful recognizes the need to find and identify killers, but not to lock down cities in order to do so.

    In order to be a free society, we have to be willing to take our knocks, including the chance that we can be killed or injured in public. We should be wary of officials who seek to suspend liberties. We know that when thousands of Americans were killed in New York, many of us lost liberties which we have never seen restored.

    Although your blog implies the terrorists hold complete blame for the authorities’ response to the bombing, I believe you are failing to see the degree to which authorities take advantage of public fear to expand their powers. As Machiavelli suggests in his writing, the power of fear to motivate people in support of the prince is ever present where there is a powerful prince.

    And as recent reports that CIA cash payments made to President Karzai ended up in Taliban bank accounts suggest, it’s really hard to know who’s on The Company payroll and who’s not.

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  3. 3. CBacon 7:17 pm 04/29/2013

    Regarding what paulus said, it was a certain public official that stated “Never let a good disaster go to waste.” The police forces were giddy that they got free run of the streets to show what power they had. Public officials were happy to oblige this.
    The secret service even got in on the action by making an appearence. Why were they there? They are supposed to be guarding the president, not helping to investigate general crimes.

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  4. 4. paulus 11:13 pm 04/29/2013

    What is truly extraordinary regarding the Boston lockdown is its normalcy, its reflexive support among the citizens, with little regard to its origins. For what a citizen of thirty years ago would find extraordinary in contemporary life is the degree to which a prison institutional practice– the lockdown –has come to be regarded as an acceptable practice in civil society with little discussion of its implications to our democratic system.

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  5. 5. PatriciaJH 11:40 pm 04/29/2013

    Note that not counting the number maimed decreases our sense of the seriousness of the event — I think it was around twenty?

    After 9/11, I noted that (IIRC) 600,000 planes had landed safely, worldwide, and that flying was still the safest means of travel per passenger mile. I did take stock, and stopped commuting to work on Route 128, as it was the riskiest thing I did that I didn’t enjoy; I went by back routes instead, somewhat slower but much lower risk and also more pleasant.

    However, I too sat at home that Friday thinking about risk. Suppose we’d gone about business as usual, and that exceedingly foolish and misguided young man had taken yet another pressure cooker full of crap to the Watertown Registry of Motor Vehicles, with its long, long lines of people who generally feel that their business there is urgent and can’t be delayed. (We now know he was in no shape to do that, and he’d left the last one behind in the SUV, but we didn’t know that then.)

    * It would have been an indoor explosion, with walls containing the blast; my understanding is that even those shielded by bodies from the shrapnel would have been much more injured by the blast.
    * There would NOT have been numerous experienced first responders present — the Marathon had many present as volunteers at aid tents; a group of active-duty soldiers had just finished the course; the area itself is close to a number of hospitals; also the sheer number of people at the Marathon would mean a high number of knowledgeable people nearby — not true at the Watertown Mall;
    * Without the large number of spectators, and with the indoor blast effects, there would be a much higher ratio of critical injuries to capable rescuers.
    * There would not have been ambulances standing by for runners and also for the large number of spectators at the event;
    * There would not have been aid tents already set up nearby;
    * It would not have been immediately geographically next to all those high level trauma-capable hospitals. Mount Auburn simply would not be able to handle everyone.
    * It would likely not have been just at hospital shift-change, a happenstance that meant receiving hospitals had double the staff immediately at hand.
    * By Friday, we knew these mitigating factors had greatly reduced loss of life.

    My guess — based on what’s been said about the Marathon injuries — is that in my RMV scenario, fifteen to thirty might die, and many more would be injured.

    My own suspicion at the time was that he’d be found cowering under someone’s porch, unglued, injured, and lost without his mastermind. Or in someone’s shrubbery. But I sure didn’t like the alternate worst-case scenario — and I did notice that public safety officials took care to see that crowds didn’t gather even outside the shelter-in-place area, canceling a Lexington gun rally.

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  6. 6. syzygyygyzys 1:04 am 04/30/2013

    The point to the lockdown WAS TO CATCH THEM!

    All these high minded musings about how we apes think and evaluate risk completely missed the point. We didn’t need to stop and ponder how many terrorists could dance on the head of a pin. We needed to catch them and we did. They have and will be selected against.

    The idea that if we just cleaned up the mess and went about our business the terrorists would eventually get bored and quit killing us is pure nonsense. The author does get it right at the end. At the end he effectively says, “Eh. I don’t know?” It sure took a lot of words to get there.

    Some of you should think about how the strategies you espouse would work out for you personally in the presence of real danger. My belief is that you would be selected against.

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  7. 7. Kevbonham 9:20 am 04/30/2013

    @Paulus – when I ask google for the definition of “tragedy,” it tells me:

    An event causing great suffering, destruction, and distress, such as a serious accident, crime, or natural catastrophe

    I certainly think this definition applies to the Marathon bombing. That said, I actually agree the response was a bit over the top – the reason I researched this piece is because in the moment, as I was living through it, it didn’t seem like an overreach. I was genuinely scared, and thinking back, I wanted to understand why I was so afraid of something that I would be willing to go along with such extraordinary actions as a city-wide lockdown.

    @PatriciaJH – You’re right, there were plenty of potential risks still outstanding, but my point here is that we aren’t willing to incur the costs (hundreds of millions) to *actually* prevent 30 deaths due to other causes, why were we willing to do so to *potentially* prevent 30 deaths due to a bombing?

    @syzygyygyzys – My point is not that if we ignored them, they would go away. I’m wondering why we don’t lock down cities to catch other types of murderers (like that triple homicide I mentioned). Why don’t we call in the SWAT and National Guard to catch the gang members perpetrating all of the inner-city violence that kills hundreds or thousands of young people every year?

    The response in Boston was substantially different than our responses to other types of violence or other causes of death. I think it’s worth trying to understand why. Maybe our response in Boston was actually the correct one, and the moral to the story is that we *should* call in SWAT more often. I don’t think I really know the answer.

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  8. 8. paulus 9:57 am 04/30/2013

    @kevbonham I think it is important we regard tragedy as a slow train wreck, tied to the character of individual, or set of individuals. It is at the basis of drama, and informs our feelings of unimaginable loss in the stories of Oedipus, Hamlet, and Macbeth. A death at a sporting event is tragic by comparison. They are not the same thing, but when a bombing is constantly referred to as a ‘tragedy’ it can evoke an over the top response.
    In spite of the terrible aspect of the destruction of the twin towers a decade ago, I never heard the media refer to the attack as a ‘tragedy’. Our response was robust, rather than characterized as a series of events that strips us of our dignity, which is what tragedy does. In response to such perceived degradation, human beings feel a threat to their survival.
    I suggest we consider the Boston response an over-reach in considering what you are recommending, that we use SWAT teams and engage in neighborhood or city-wide lock downs when authorities perceive a necessity to do so. It seems to me the idea of locking down cities and conducting house-to-house searches comes close to quartering soldiers in homes in peacetime. Of course, there are other considerations that were never brought to the fore, such as warrantless searches, which we seem to be immune to after the Patriot Act.
    After all, as one respondent above notes, we had to catch the criminals. Yet what is the legacy of an acquiescent population allowing the city to be turned into a citadel? As Harold Lasswell suggested decades ago, societies can become garrison states and lose their liberties in pursuit of absolute security. Is it worth the price?

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  9. 9. syzygyygyzys 10:32 am 04/30/2013


    Here’s your answer.

    If these other “perps” you speak of were known by their pictures, had just executed a cop, and carjacked a vehicle with a live cell phone which could be tracked to show where they were, the police would do EXACTLY the same thing.

    Think about it.

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  10. 10. Kevbonham 12:00 pm 04/30/2013

    @ Paulus – Here is a google news search for “tragedy” in the month after 9/11 ( There are a TON of hits, in USA today, NYT, WaPo etc.

    And you think the PATRIOT Act, warrentless wiretapping, the security state that we’ve lived under for the past 12 years, and a 10-year war that we were lied to in order to enter are merely “robust responses?”

    @ syzygyygyzys – I have thought about it, and I don’t think you’re correct. Saying that, if the details were exactly like this crime, the response would be the same is essentially a tautology.

    Do you think that our response to all types of crime is actually proportionate to its severity? If not, it’s worth understanding *why* not.

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  11. 11. syzygyygyzys 12:24 pm 04/30/2013


    I don’t think “tautology” means what you think it means.

    I’m not saying the details would have to mirror the situation in Boston. I am saying if the police had identity and real-time perp tracking on random murderers, the police response very likely would be similar. Your attempts to conflate the terrorists and gang members are specious. Were you even aware of some of those details? Why don’t you tell us what your ideal police response to that situation would have been? I’m very curious to know.

    I leave it to other readers to make their own evaluation.

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  12. 12. Quantumburrito 3:22 pm 04/30/2013

    syzygyygyzys: Consider this: There are parts of LA and any number of cities where heavily-armed drug cartel members are on the loose. Do the police submit parts of these cities to a lockdown on a regular basis and conduct house-to-house searches? The real question is, what made this guy so *radically* different from other dangerous criminals? In my opinion, nothing in particular. Ron Paul has written an op-ed in which he says that subjecting entire cities to military-style lockdowns sets a dangerous precedent.

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  13. 13. syzygyygyzys 3:57 pm 04/30/2013

    Another Ron Pauler? To quote Dr. Seuss,”Save us from those pale green pants with nobody inside.”

    Sorry, but I’m trying to keep the quotes from literature they may have read.

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  14. 14. Quantumburrito 4:03 pm 04/30/2013

    Ah, the classic gambit: Ad hominem devoid of actual arguments.

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  15. 15. paulus 4:22 pm 04/30/2013

    Kevin, I enjoyed the dialogue with you, but I don’t know if I have made myself clear. I agree with you that many of the actions we took after September 11 were over-reactions. What I am suggesting is there was not a 100% trope that ran through all the news feeds calling September 11 a ‘tragedy’. It was called a horror, a terror attack, and like terms in the media. What was different in Boston was that almost everyone referred to it as a ‘tragedy’.
    Of course you can google ‘tragedy’ and find that used in some coverage of the events of a dozen years ago, yet it was not the term nearly universally used by the media this time. Perhaps the nation is still raw after the Newtown massacre, but for what ever reason the bombing became known as a tragedy.

    I have to disagree with using google to define a word. But, then, I am old school: render unto google, what is google’s; render unto webster, what is the webster’s…

    My take on Boston is different from others, as someone said on this string, I would be one of those ‘selected against’ in the face of real danger.

    Well, that is a bit problematic, since I have already been selected against when we went to war a decade ago.
    I had to ask why we were going to war against a country that didn’t attack us, but was shouted down because most people were afraid because the government lied to them about the danger we were facing from Hussein.

    This is called group-think. It is a tyranny of the majority. It doesn’t matter to me that eventually people come around. What I see is that people can be herded into a group mentality, and we see this in the language we use. We begin using ‘us’ and ‘them’ language when there is only really ‘us’.

    Because we have accepted the division between us and them, then it is okay to arrest someone, and not let them see a lawyer. Or to try them in a military tribunal. Or to round up numbers of them and put them in camps, like we did with Fred Korematsu and other Americans during World War Two. It doesn’t matter to us at the time because Korematsu wasn’t one of us, he was one of them.
    But it is only when those kinds of divisions become visible in a society that it becomes socially acceptable to curtail liberties which are at the heart of our civilization. If we have to destroy liberty to save a civilization based on it, is it worth saving?

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  16. 16. syzygyygyzys 4:23 pm 04/30/2013

    Did I say I was talking to anyone specifically? Someone under the spell of the Prince of Insufficient Light is already beyond reason. Discussion with them is pointless. If someone wants substance, read post 6 and 9. My work here is done.

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