Why Does My Brain Treat Small Things as Emergencies?

A new manager announces a ten-minute check-in at the start of each day. The message is two lines long. By lunch, three people on the team have read it as a sign that their work is being watched, and one has started updating a résumé. The manager wanted a quicker way to hear about blockers.

Your brain treats small things as emergencies because its defenses are set like a smoke detector. A response that costs little, against a harm that would cost a great deal, should fire whenever the chance of harm passes a low threshold, and at that threshold most alarms are false (Nesse, 2005). If the same arithmetic governs the check-in, a two-line message clears the threshold.

What Is the Smoke Detector Principle?

Randolph Nesse, a physician who works on the evolutionary reasons for illness, asked why the body's defenses, such as anxiety, pain, and vomiting, so often fire when nothing is wrong. His answer treated each defense as a detector with a threshold, and asked where natural selection would set the threshold (Nesse, 2001). The setting depends on two costs. One is the cost of the response itself. The other is the cost of the harm the response protects against, if the response does not fire and the harm arrives.

In his 2005 analysis, Nesse worked the numbers for one defense. Suppose a panicked flight from a possible predator costs 300 kilocalories, and an attack on an animal that did not flee costs, on average, 300,000. The ratio is one to a thousand, so the flight pays for itself whenever the estimated chance of an attack is greater than one in a thousand. A detector set at that threshold fires 999 times for every attack it prevents, and each of those 999 is a false alarm (Nesse, 2005). He named the pattern after the household smoke detector, which is set to fire at small amounts of smoke because a missed fire costs far more than a false alarm.

How Is a Detector's Threshold Set?

The framework behind Nesse's analysis is signal detection theory, set out by David Green and John Swets in 1966 (Green and Swets, 1966). Any detector facing an uncertain signal can produce four outcomes. It can fire when the danger is real, a hit. It can stay quiet when the danger is real, a miss. It can fire when nothing is there, a false alarm. It can stay quiet when nothing is there, a correct rejection. At a given sensitivity, moving the threshold trades misses for false alarms, and the right place for the threshold depends on how often the signal occurs and on what each of the four outcomes costs.

That is how thresholds are set on purpose in fields that decide under uncertainty. John Swets, Robyn Dawes, and John Monahan showed the same arithmetic at work in medical diagnosis, weather forecasting, the prediction of violence, and aircraft inspection, where the threshold is moved according to the base rate of the condition and the costs and benefits of each outcome (Swets, Dawes and Monahan, 2000).

Why Are the Body's Defenses Set to Over-Respond?

Because the defenses are cheap and the harms are large. Isaac Marks and Nesse argued in 1994 that anxiety is an evolved defense, useful only when well regulated, and that it looks over-responsive because many false alarms cost less than one failure to respond to a great danger (Marks and Nesse, 1994). In a 2019 summary, Nesse listed anxiety, inflammation, pain, vomiting, cough, and diarrhea as defenses that each cost little relative to the harm they prevent, so that optimal regulation of every one of them produces many false alarms (Nesse, 2019).

The defense that fires at the check-in message is the stress response, the coordinated set of changes described in What Does Fight or Flight Mean at Work?, and the detector that starts it is the amygdala (Why Do I React to an Email Before I've Finished Reading It?). The response costs some glucose and an uncomfortable hour. The harm it defends against, in the environment that set the threshold, was a predator attack.

Does the Same Setting Apply to Judgments?

Yes. Martie Haselton and David Buss proposed in 2000 that where the two kinds of error have carried unequal costs over evolutionary time, selection favors decision rules biased toward the cheaper error, even at the price of more errors in total, and they called the account error management theory (Haselton and Buss, 2000). Their own data concerned how men and women read each other's intentions; the principle is general.

Haselton and Daniel Nettle then collected biases that fit the pattern. People hear an approaching sound as arriving sooner than it will, which is the cheaper error when the sound is a predator. People over-detect dangerous animals such as snakes and spiders. Their illustration, a hypothetical case with no experiment behind it, is a person who mistakes a stick for a snake many times at a small cost each time, against a person who mistakes a snake for a stick once (Haselton and Nettle, 2006). Dominic Johnson and colleagues set out the general case. Under uncertainty, when the two errors cost different amounts, a decision rule biased toward the cheaper error lowers the expected loss, so the bias is the adaptive setting (Johnson, Blumstein, Fowler and Haselton, 2013).

Ryan McKay and Charles Efferson added a limit. Unequal costs need only bias the action, the flinch or the flight, and need not bias the belief. A person can act as though the shape were a snake while knowing it is probably a stick, so a bias in what people believe needs its own explanation (McKay and Efferson, 2010).

Why Does a Two-Line Message Set Off a Large Response?

No study has applied the principle to a workplace, so what follows is the arithmetic applied to the check-in. The cost of responding, by reading the message as surveillance and bracing for it, is an afternoon of unease. The cost of the missed threat, if the check-in were the start of closer monitoring and the person had treated it as nothing, is to standing and control, the two features that produced the largest stress responses in the laboratory (Dickerson and Kemeny, 2004). If the same arithmetic governs the check-in, the ratio is lopsided in the same direction as Nesse's, the threshold sits low, and a two-line message with no stated reason carries enough ambiguity to clear it.

The threshold also moves with the stakes a person believes are in play. Spencer Lynn and Lisa Feldman Barrett showed that when people judge whether a face is threatening, the criterion they use shifts with the payoffs for each outcome and with how common threats are, in the direction signal detection theory predicts (Lynn and Barrett, 2014). Their task was faces, with no workplace examples. If the same shift applies to a message, a person who has been through two reorganizations judges the check-in against a higher base rate of threat and a worse remembered cost of missing one, so the same message clears their threshold by a wider margin, and the amygdala's tuning to the person's own needs and goals is part of why (Why Do I React to an Email Before I've Finished Reading It?).

Which Biases Can Be Read as the Same Setting?

The decision habits that make change hard (Why Is Change at Work So Hard?) can be read with the same structure. For each one there is a cheap error and a costly error, and the habit leans toward the cheap one. None of these biases appears in the lists error management theory's authors published, so the reading below extends the principle beyond the cases they describe, and the section on limits says what the extension does and does not claim.

Negativity. Negative events carry more weight than positive ones in attention, learning, and judgment (Why Does One Piece of Criticism Outweigh Ten Compliments?). Read as a detector setting, under-weighting a threat is the costly error and over-weighting a threat is the cheap one.

Loss. Losses loom larger than gains (Kahneman and Tversky, 1979), and a loss is the outcome the detector exists to prevent (Why Does Losing Hurt More than Winning Feels Good?).

The current option. The option labeled as the current state draws more choices (Samuelson and Zeckhauser, 1988), and Why Does Doing Nothing Feel Safer than Changing? carries the finding. Read this way, the current option's harms are already known and costed, the new option's harm is unknown, and an unknown harm clears the threshold, which is one reason doing nothing feels safer.

Unknown odds. When the odds are unknown, the chance of harm cannot be estimated, and ambiguity engages the amygdala more than known odds do (Hsu, Bhatt, Adolphs, Tranel and Camerer, 2005; Why Do Teams Choose a Known Problem over an Unknown Fix?).

Familiarity. Read as a detector setting, each exposure to something that did no harm is a correct rejection on record, so the familiar option carries evidence of safety that the new one lacks (Why Does Something Feel Safer Just Because It Is Familiar?), and a brain that predicts what it will see from what it has seen treats the unpredicted as a signal (Why Does My Brain React to What It Expects Instead of What Happens?).

Ownership and effort. Giving up something you own, or something you built, is a loss of a resource already in hand, which is the costly side of the asymmetry; overvaluing what is yours and defending what you helped build both lean that way.

The first number, sunk costs, and confirmation. Holding to the first number offered, continuing to fund what is not working, and reading new data in favor of the current belief each keep a decision close to what is already known, and on this reading abandoning the known is the costly error.

What Can a Person Do with an Over-Cautious Detector?

The threshold is a setting, and the setting depends on costs that can be checked. In the check-in scenario, the costly error, as stated, is being monitored without noticing. Put a number on it. What would closer monitoring change about the next month, and what would the person do about it if it arrived? Then price the false alarm. An afternoon of bracing, a résumé updated for nothing, a cooler relationship with a new manager, and a check-in attended in a defensive posture for weeks. In Nesse's example the false alarm cost 300 kilocalories. At work it costs relationships and decisions, which moves the ratio and raises the threshold at which responding pays.

Signal detection theory's second variable is the base rate, and it can be checked too. How often has a two-line message from a manager turned out to be surveillance? Lynn and Barrett's finding is that people's criteria move with the base rate they believe in (Lynn and Barrett, 2014), so if the same shift applies, answering the question from the record should move the setting.

What the Smoke Detector Principle Is

Smoke detector principle: Randolph Nesse's account of how natural selection sets the threshold of a defense. A defense should fire whenever the estimated chance of harm exceeds the ratio of the response's cost to the harm's cost. For a cheap response against a large possible harm, that threshold is very low, so the defense fires often when nothing is wrong, and at that setting most of its alarms are false (Nesse, 2001; Nesse, 2005).

Does the Principle Explain Every Bias?

No, and the limits are in the sources. Nesse's analysis is about the regulation of bodily defenses, and its figures are for a flight from a predator. Error management theory extends the same logic to judgments, and its authors' own examples are approaching sounds, dangerous animals, and a set of social inferences (Haselton and Nettle, 2006). Reading negativity bias, loss aversion, status quo bias, ambiguity aversion, and the familiarity effect as the same cost asymmetry is an extension of the theory, and anchoring, sunk costs, and confirmation bias sit furthest from its cases. Johnson and colleagues name cognitive constraints as the rival account for biases in general, limits of the machinery that produce errors with no cost asymmetry behind them (Johnson, Blumstein, Fowler and Haselton, 2013).

McKay and Efferson's point stands against the strongest version of the account. A low threshold explains why a person flinches at a message. It does not by itself explain why the person comes to believe the message is surveillance, because the cost asymmetry needs only to bias the flinch (McKay and Efferson, 2010). The belief has other sources, among them the response to ambiguity (Why Do Teams Choose a Known Problem over an Unknown Fix?) and the person's history with managers. The detector itself is also broader than a threat detector, since the amygdala responds to novel, ambiguous, and positive events as well (Why Do I React to an Email Before I've Finished Reading It?).

Johnson and colleagues also name the mismatch. A threshold tuned to ancestral costs and base rates misfires when the costs and base rates have changed (Johnson, Blumstein, Fowler and Haselton, 2013). At work the false alarm is rarely free and the costly error is rarely a predator attack, so a setting that was optimal for the predator is, on this reading, set too low for the check-in.

Before reacting to the next small change at work, write down the two errors, what it would cost you if the worry were right and you did nothing, and what it would cost you if it were wrong and you acted on it.

FAQ

Is it normal to overreact to small things at work?

Yes. The body's defenses are set to fire at a low threshold because the response is cheap and the harm it prevents is large, and at that setting most alarms are false (Nesse, 2005). The same cost asymmetry biases judgments toward the cheaper error (Haselton and Buss, 2000). A small ambiguous cue at work clears the threshold if the same arithmetic applies.

What is the smoke detector principle?

Randolph Nesse's account of how natural selection sets a defense's threshold. In his worked example, a 300-kilocalorie flight against a 300,000-kilocalorie attack should fire whenever the chance of attack is greater than one in a thousand, which produces 999 false alarms for every attack prevented (Nesse, 2005).

Does everyone's threshold sit in the same place?

No. The criterion people use to judge a threatening face shifts with the payoffs they expect for each outcome and with how common they believe threats to be (Lynn and Barrett, 2014), and the amygdala's responses are tuned by a person's own needs, values, and goals (Why Do I React to an Email Before I've Finished Reading It?). Two people read the same message against different base rates and different remembered costs.

Why do we over-detect danger?

Because a miss costs more than a false alarm. In signal detection theory, moving a detector's threshold trades misses for false alarms, so where the miss is expensive the threshold is set low and the false alarms are accepted (Green and Swets, 1966). Anxiety, pain, and the other defenses are regulated that way (Nesse, 2019).

How does this connect to the biases that make change hard?

Each bias leans toward one of two errors. Negative events carry more weight than positive ones (Why Does One Piece of Criticism Outweigh Ten Compliments?), losses loom larger than gains (Why Does Losing Hurt More than Winning Feels Good?), and the current option draws more choices (Why Does Doing Nothing Feel Safer than Changing?). On the reading above, in each the costly error is the one the detector exists to prevent, and the habit leans away from it.

Does the principle mean the brain believes the threat is real?

No. Unequal costs need only bias the action, so a person can flinch at a shape while knowing it is probably a stick, and a bias in belief needs its own explanation (McKay and Efferson, 2010). The flinch at a two-line message and the belief that it is surveillance are separate events with separate sources.

Is the setting right for work?

No. A threshold tuned to ancestral costs and base rates misfires when both have changed (Johnson, Blumstein, Fowler and Haselton, 2013). At work the false alarm costs relationships and decisions and the miss rarely costs anything like a predator attack, so the ratio that set the threshold low has moved.

What can I do about an over-cautious brain?

Check the two inputs the threshold depends on. Price the costly error and the false alarm in the situation in front of you, and check the base rate against the record, since people's criteria for judging a threat move with the base rate they believe in (Lynn and Barrett, 2014). Both move the threshold toward where the present costs put it.

If you're leading a change and want people to keep moving through it, The DANCE System gives you 29 tools for planning and communicating the change in five phases, from defining it to keeping it in place after launch.

Related Posts:

What Does Fight or Flight Mean at Work?

Why Do I React to an Email Before I've Finished Reading It?

Why Is Change at Work So Hard?

Why Does Doing Nothing Feel Safer than Changing?