Maybe Our Biases are Rational

by | Oct 21, 2020

That looks like a long way down!

Adaptive Rationality

That we are hardwired to make irrational decisions due to our ingrained biases and heuristics has become a hot topic over the past few decades. In fact, over the past 18 years three Nobel Prizes in Economics have been awarded for work on exposing how biases shape our decision-making: Daniel Kahneman (2002 – he’s actually a psychologist), Robert Shiller (2013), and Richard Thaler (2017).

While we all have inherent biases such as loss aversion and the endowment effect, evolution provides a good reason why we have these biases. The idea that our biases serve an evolutionary purpose is broadly referred to as adaptive rationality. Within adaptive rationality, error management theory provides an explanation for many of our biases.

Error Management Theory

Error management theory posits that our biases actually help us make better decisions by directing us towards safer results. It is based on the concept that there are asymmetries in costs of errors and that we’ve evolved to prefer decisions that avoid costly errors even if these biases result in more, but less costly, errors.

A leading research paper summarizes the concept as follows: “Under conditions of uncertainty and asymmetric costs of ‘false-positive’ and ‘false-negative’ errors, biases can lead to mistakes in one direction but – in so doing – steer us away from more costly mistakes in the other direction. For example, we sometimes think sticks are snakes (which is harmless), but rarely that snakes are sticks (which can be deadly).”

Smoke Alarms as an Analogy

The classic example demonstrating how it sometimes makes sense to be biased towards an error is the design of smoke alarms. Having a false negative — meaning failing to detect a fire — is an extremely costly error, while having a false alarm usually is not costly — just irritating. So, smoke alarms are engineered to be biased towards having false alarms and so that they always go off when there’s really a fire. This is a good example of how error management theory works: its better to experience a frequent error that is not costly so that a costly error can be avoided.

Error Management Theory in the Real World

Why Men Tend to Think Women Are More Interested in Them Than Really Is the Case.

Studies have shown that men overestimate sexual interest from women. Men tend to think a women is being flirtatious when she’s actually just being nice and not expressing sexual interest. Evolutionary psychologist Martie Haselton of UCLA explains the evolutionary basis for this bias as follows:

For an ancestral man, failing to detect sexual interest in a woman resulted in a missed reproductive opportunity, which was highly costly to his reproductive success. The opposite error (believing that a woman was interested when she was not) was perhaps a bit embarrassing, but probably was less costly overall. Thus, error management theory predicts that natural selection designed a bias in men toward slightly overestimating a woman’s sexual interest in order to reduce the likelihood of a missed sexual opportunity; this leads modern men to “overpercieve” women’s sexual interest.

Flowers Don’t Cut It: Females Underestimate Male Relationship Commitment

Males aren’t the only ones with reproductive biases. Error Management Theory explains why women are skeptical of male expressions of commitment during courtship. While evolution favors men spreading their genes by jumping on sexual opportunities, the opposite is true of women. Females invest heavily in each offspring through the physical stress of pregnancy and birth and then through nursing and child-rearing. As such, women must be very choosy in selecting their mates. In addition to genetic fitness, historically women also needed commitment from their mate that they would remain around to protect and provide for her and her child. Here’s an explanation of this concept from Martie Haselton:

Women must predict a man’s tendency to invest from his behaviors, and therefore their judgments
will be susceptible to some degree of error. Here again, there is an asymmetry in the costs of the errors in the judgment task. Judging that a man will commit and invest when he actually will not (a false positive error) could result in the woman consenting to sex and being subsequently abandoned. In harsh ancestral environments, this literally could have been deadly to the woman’s offspring. The opposite error—believing that the man
is not committed when he actually is (a false negative)—would typically result only in a delay of reproduction for the woman, which would tend to be less costly. Error management theory therefore predicts that women will tend to be skeptical of men’s commitment, especially during the early phases of courtship. This prediction has been tested by comparing men’s and women’s impressions of male courtship behaviors. Relative to men, women express skepticism about a variety of male courtship tactics, including buying flowers, cooking a gourmet dinner, and saying I love you.

A Few Other Examples

Error Management Theory explains why we are wary of strangers and are careful about trying new foods (who knows if they are poisonous), why we perceive outside noises to be threats (it’s less costly to assume it’s a predator when it’s really just the wind). Here’s a few others:

The visual descent illusion. “To illustrate: Have you ever thought it would be no problem to jump off of a ledge, but as soon as you stood up there, it suddenly looked much higher than you thought? The visual descent illusion states that people will overestimate the distance when looking down from a height (compared to looking up) so that people will be especially wary of falling from great heights—which would result in injury or death.” Source.

The auditory looming bias: “Have you ever noticed how an ambulance seems closer when it’s coming toward you, but suddenly seems far away once it’s immediately passed? With the auditory looming bias, people overestimate how close objects are when the sound is moving toward them compared to when it is moving away from them. From our evolutionary history, humans learned, ‘It’s better to be safe than sorry.’ Therefore, if we think that a threat is closer to us when it’s moving toward us (because it seems louder), we will be quicker to act and escape. In this regard, there may be times we ran away when we didn’t need to (a false alarm), but wasting that time is a less costly mistake than not acting in the first place when a real threat does exist.” Source.


  1. Biases GENERALLY will keep you alive! Of late, our educational system has strived to eliminate, many biases that not only keep young people safe but also FREE! Americans traditionally have perceived INDIVIDUAL FREEDOM as being vital to the human experience, whereas the system has been trying to educate students to believe that PRIVILAGES of others, often based on identity politics, is the more important!

  2. This may be the best IFOD yet.

    • The last few have definitely been memorable (says my recency bias). Great work John! This really hit my soft spot for human biases.


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