Heuristics Basics

I. What Heuristics Actually Are

A heuristic is a cognitive shortcut. The brain uses heuristics to make decisions faster than full analysis would allow, trading accuracy for speed. Most of the time, this works well; humans evolved in environments where fast decisions kept you alive and slow decisions got you killed. Some of the time, this works badly; the heuristics that served Pleistocene environments produce predictable errors in modern ones.

The popular framing often conflates heuristics with biases. They are related but distinct:

• Heuristic: A general decision-making shortcut. Examples: judge frequency by how easily examples come to mind (availability), judge probability by how similar something is to a typical case (representativeness), use the first number you hear as a reference point (anchoring).
• Bias: A systematic departure from accurate judgment that often results from heuristic application. Examples: overestimating the frequency of dramatic events (availability bias), assigning probability based on resemblance rather than base rates (representativeness bias), being unduly influenced by irrelevant numbers (anchoring bias).

Heuristics are cognitive tools; biases are the systematic errors that result when the tool is misapplied. The same heuristic can produce an accurate judgment in some contexts and systematic error in others.

Daniel Kahneman and Amos Tversky’s research established the heuristics-and-biases tradition in the 1970s. Their work documented systematic departures from rational decision-making across multiple domains and culminated in Kahneman’s 2002 Nobel Prize in Economics. The 2011 book Thinking, Fast and Slow is the accessible synthesis.

II. System 1 and System 2

• System 1: Fast, automatic, intuitive, emotional, effortless. The “gut feelings” and snap judgements. Operates continuously below conscious deliberation. Where heuristics live.
• System 2: Slow, deliberate, analytical, logical, effortful. The conscious reasoning that engages when System 1 produces an answer you don’t trust or when the situation demands more careful consideration. Where formal reasoning lives.

The two systems usually operate together. System 1 produces a candidate answer; System 2 either accepts it (most of the time) or intervenes to override (rarely). The fact that System 2 intervenes rarely is what makes us efficient; it’s also what makes us systematically biased.

Practical implications.

System 2 is metabolically expensive. Sustained System 2 engagement is genuinely tiring. The “decision fatigue” framing oversells the effect, but the underlying phenomenon (extended deliberate thinking is more demanding than automatic processing) is real.

System 1 is largely unconsciously trained. Your snap judgments reflect the patterns your brain has learned, often without your deliberate input. Cultural training, family patterns, professional expertise, and broader environmental exposure all shape what System 1 produces.

System 2 can train System 1 over time. The classic case is expertise development. The chess master’s intuitions about board positions are System 1; they were built through years of System 2 study that gradually became automatic.

Heuristics belong especially to System 1 thinking, while System 2 thinking uses more conscious and deliberately manipulable mental models. This is the distinction that anchors the Heuristics Basics page in System 1 territory while Mental Model Basics develops the System 2 tools.

The System 1/System 2 distinction is useful as a high-level model but oversimplifies the underlying neuroscience. The two systems are not literally separate brain modules; they are heuristic labels for different processing styles that engage different neural circuits in overlapping ways. Kahneman himself acknowledged the simplification. Treat the framework as a useful map rather than a precise description.

III. The Cognitive Biases Catalogue

The list of documented biases from the heuristics-and-biases literature. Brief annotations on each.

• Selective perception: Noticing what fits your existing beliefs and missing what doesn’t.
• Confirmation bias: Actively seeking information that supports your existing views and dismissing information that contradicts them. One of the most robust findings in the literature.
• False-consensus effect: Assuming others share your views and behaviours more than they actually do.
• Cognitive inertia: The inability to see perspectives other than your own. Often manifests as inability to genuinely model how someone with different priors would interpret the same information.
• Conservation bias: Resistance to changing established beliefs even when evidence warrants the change.
• Information bias: Seeking information that doesn’t actually affect the decision being made. The illusion of preparation through data accumulation.
• Recency illusion: Believing something is recent simply because you noticed it recently. Often produces false claims about declining standards or new phenomena.
• Clustering illusion: Seeing patterns in genuinely random data. The brain is pattern-matching machinery; it produces patterns even when none exist.
• Bandwagon effect: Adopting beliefs or behaviours because they’re popular. The social proof dynamic operating below conscious deliberation.
• Blind-spot bias: Recognising biases in others while failing to recognise the same biases in yourself. Recursive and difficult to address.
• Anchoring: Attachment to the first piece of information encountered. Even arbitrary numbers can influence subsequent estimates.
• Cognitive ease: Believing claims expressed in simpler, more familiar, or more rhyming language. The mere fluency of a claim affects how truthful it feels.
• Priming: Suggestions that direct attention toward specific information that gets used in subsequent decisions without conscious recognition.
• Intuitive heuristic substitution: Answering an easier question than the one you were actually asked. The brain substitutes a tractable problem for the difficult one and reports the answer as if it solved the original.

IV. The Replication Question

The replication crisis context: Psychology has experienced a replication crisis since approximately 2011. The Reproducibility Project’s 2015 study attempted to replicate 100 psychology studies and successfully replicated less than half. Multiple bias findings have been affected.

Findings that have held up

• Confirmation bias (robust across domains)
• Anchoring effects (effects sizes reduced but direction preserved)
• Availability heuristic (general phenomenon replicates)
• Loss aversion (general phenomenon replicates with some caveats)
• Hindsight bias (robust)
• Status quo bias (robust)
• Endowment effect (replicates)

Findings that have failed to replicate

• Most priming research (particularly social priming effects from the early 2000s)
• Ego depletion (Baumeister’s willpower-as-finite-resource framework)
• Power posing effects (Carney/Cuddy research)
• Many specific cognitive bias effects in their originally-reported magnitudes

Findings under active dispute

• Implicit association tests (predictive validity contested)
• Stereotype threat (effect sizes smaller than initially reported)
• Specific bias intervention effectiveness

The general phenomenon of systematic biases in human judgement is well-established. Specific bias effects vary in robustness; some are nearly universal, others are more context-dependent than the popular literature suggests. Take the biases catalogue as a useful sensitisation tool, not as a settled scientific consensus.

Kahneman himself acknowledged in 2017 that some of the research discussed in Thinking, Fast and Slow (particularly the priming chapter) has not replicated reliably.

V. The Gigerenzer Counter-Position

Gerd Gigerenzer’s research has argued that what looks like bias from a formal-logic standpoint often represents adaptive use of fast-and-frugal heuristics that work well in their native environments.

The ecological rationality framing: Heuristics evolved for specific environments. A heuristic that produces “biased” answers in laboratory conditions may produce accurate answers in the real conditions it evolved for. Treating heuristics as errors to correct may misunderstand what they are doing.

Examples from the research

• The recognition heuristic (judging which of two options is larger by which one you recognise) outperforms more elaborate analysis in many real-world prediction tasks
• Take-the-best (using only the most predictive cue and ignoring others) often outperforms multiple-regression models in environments with limited data
• Gut feelings of experienced practitioners often outperform formal decision-support systems in domains where the experienced practitioner has trained intuitions

Mental model work is not just about replacing heuristics with formal reasoning. Sometimes the heuristic is the right tool. The skill is knowing when to use which.

VI. WEIRD Brains and Evolutionary Mismatch

The evolutionary biology framing on why heuristics that evolved for ancestral environments produce systematic errors in modern ones. This material draws on the framing in A Hunter-Gatherer’s Guide to the 21st Century by Heather Heying and Bret Weinstein.

• The WEIRD brains observation: Western, Educated, Industrialised, Rich, Democratic populations show measurably different cognitive patterns than non-WEIRD populations. Clean, square, climate-controlled environments may be impairing certain visual perception abilities, such as recognising that two identical-sized lines with opposing arrowheads are in fact the same size (the Müller-Lyer illusion).
  • Alternatively, this can be framed as adaptation rather than loss. The unnatural symmetry of modern environments has restructured WEIRD brains in ways that show up in cognitive testing.
• The lactase persistence parallel: Lactose tolerance evolved as a functional substitute for vitamin D promoting calcium uptake in high-latitude populations. Among desert peoples, the ability to digest milk allowed avoiding dehydration. Lactase persistence was born of a particular environmental condition that moved onto a genetic layer.
• The false dichotomy: The nature-versus-nurture framing is disruptive because it interferes with a more nuanced understanding of the evolutionary forces shaping us. The change in susceptibility to optical illusions seen in WEIRD countries is no less evolutionary than the change in ability to digest dairy. The latter has a genetic component; the former may not. Both are equally evolutionary outcomes.
• The implications question: Carpentered corners create greater susceptibility to certain optical illusions. Over-reliance on chairs creates negative health outcomes. What might deodorants and perfumes have done to our ability to smell the signals emitted by our bodies? What might clocks have done to our sense of time? What have aeroplanes done to our sense of space, or the internet to our sense of competence? What have maps done to our sense of direction, or schools to our sense of family?

Each one names a specific way that modern environmental features may have altered cognitive capacities that evolved for different conditions.

VII. Trade-offs as Foundational

In biological systems, you cannot have everything optimised simultaneously. Trade-offs are universal.

Types of trade-offs

• Allocation trade-off: Many things in biology are zero-sum (finite resources). Something has to give. Energy allocated to one function is not available for another.
• Design-constraint trade-off: These are insensitive to supplementation. You cannot add more of something to solve the problem. A bat can specialise in flying fast or flying agile, or be a generalist; it cannot maximise all three simultaneously.
• The human exception (partial): Humans have avoided the design-constraint trap by building outside ourselves. We are a broadly generalist species with the capacity for individuals and cultures to specialise deeply in myriad contexts and skill sets. The cultural and technological extension allows us to access specialised capacities without each individual paying the trade-off cost.
• The Cornucopianism trap: Despite our cleverness, we cannot evade all trade-offs. Cornucopianism is the framing that imagines a world so full of resource and human ingenuity that trade-offs no longer rule. This is a mirage. Related to Cornucopianism (or fueling it) is the Sucker’s Folly: the illusion that we have conquered trade-offs by being blinded with the richness and opulence of short-term gains. The trade-offs are still there; the cost for the apparent wealth will be paid, either by those who live elsewhere or by our descendants.
• The upside: Trade-offs are unavoidable, but the unavoidability has a remarkable upside: it drives the evolution of diversity. Different organisms specialise for different niches because no single organism can be optimised for all conditions. The same applies to human cultures, professions, and individuals. The trade-offs that constrain us also produce the variety that makes us collectively adaptive.
• The biological example: Photosynthesis evolved in multiple forms because different environments imposed different constraints. C3 photosynthesis (used by most plants) works well under moderate conditions but loses water through open stomata when sunlight is available. CAM photosynthesis (used by cacti and orchids) separates carbon dioxide intake from sunlight use, allowing plants to conserve water in arid environments. CAM is more metabolically expensive but wins in environments where sunlight is plentiful and water is not. The trade-off between water conservation and metabolic efficiency drives the evolution of multiple photosynthetic strategies.

When you encounter situations where someone claims to have eliminated a fundamental trade-off, be sceptical. Usually, the trade-off has been hidden, externalised, or deferred rather than eliminated.

VIII. The Smell-as-Warning-System Problem

The evolved warning system: We are born with basic rules of thumb about what we should and shouldn’t eat. A peach smells good. A clam sitting in the sun smells bad. Grilled meat smells good. Carrion smells bad. These rules are an initial guess at the net value of a potential food.

If we stopped there, a lot of nutritious edible things would be missed. The evolved secondary system allows us to remap foods according to empirical information picked up from kin (via culture) or discovered in hunger-driven desperation (via consciousness). We acquire tastes for coffee because it stimulates us, for beer because it carries nutrition with a longer shelf life than bread, and so on.

The smell-good/smell-bad heuristic works well for whole foods in ancestral environments. It fails for several modern categories.

• Failure mode 1: solvents: Many solvents smell good to some people. Smelling them is sufficient to cause physiological harm. The smell-good heuristic says “this is fine” when the substance is actually neurotoxic.
• Failure mode 2: truly toxic substances with no smell: Natural gas and propane have no smell humans can detect. Each can concentrate in ways where the smallest spark causes a massive explosion. Before being piped into homes, these gases have tert-Butyl mercaptan added to give them a unique sulphurous smell that we easily recognise and find alarming. The artificial smell signal compensates for the failure of the evolved smell warning.
• Failure mode 3: carbon monoxide: Our CO2 detectors are so ancient and deeply wired that even people with brain damage to the amygdala (who don’t panic under other fear-inducing circumstances) find themselves triggered into panic by high concentrations of CO2. Carbon monoxide is far more dangerous; it binds to haemoglobin, displaces oxygen, and brings a quiet sleep from which people do not wake. We have no internal detector for it because the need is primarily modern, a consequence of industrial combustion. The value of a CO detector is simply too recent to be in our hardware yet.
• The general principle: Smell is no longer a sufficient early warning system for hazards because detection and harm are now simultaneous in many cases. We face novel levels of novelty, and natural selection cannot keep up. The same pattern operates across multiple cognitive and perceptual systems; the heuristics that worked in ancestral environments produce predictable failure modes in modern ones.

IX. The Corrective Lens

Practical guidance for navigating the mismatch between evolved heuristics and modern environments.

• Become skeptical of novel solutions to ancient problems: Especially when the novelty will be difficult to reverse if you change your mind later. New and audacious technologies (from experimental surgery, to the cessation of human development using hormones, to nuclear fission) may be wonderful and risk-free. But chances are, there are hidden and not-so-hidden costs.
• Recognise the logic of trade-offs and learn to work with them: Division of labour allows human populations to beat trade-offs that individuals cannot. By specialising in different habitats and niches, the human species beats trade-offs that no single population can.
• Become someone who recognises patterns about yourself: Hack your habits and physiology. What stimulates you to eat? To exercise? To check social media? Understanding the patterns in your behaviours gives you a better chance of controlling them. This connects directly to the Habit work.
• Look out for Chesterton’s Fence and invoke the Precautionary Principle when messing with ancestral systems: “Just because you can, doesn’t mean you should.” Chesterton’s Fence: before removing something whose function you don’t understand, find out why it was put there in the first place. Many ancestral systems exist for reasons that aren’t immediately obvious; removing them often produces unforeseen consequences.

X. Confirmation Bias and the Falsification Principle

Drawing on Yuval Noah Harari’s 21 Lessons for the 21st Century. The observations on epistemology.

• Calibration on the source: Harari is a popular synthesiser whose work has accumulated criticism from academic historians for the “history as dramatic stories” framing that sometimes oversimplifies. The 21 Lessons content discussed here is mostly sound observational psychology and epistemology; broader claims in Harari’s work warrant more independent verification.
• Confirmation bias revisited: What a person wishes, they also believe. What we believe is what we choose to see. Looking for confirmations of long-held wisdom is a deeply ingrained mental habit, both energy-conserving and comfortable. It runs against the scientific process, which is designed to root out precisely the opposite.
• The falsification principle: The modern scientific enterprise operates under the principle of falsification: a method is termed scientific if it can be stated in such a way that a defined result would cause it to be proven false. Pseudo-knowledge and pseudo-science operate by being unfalsifiable. As with astrology, we are unable to prove them either correct or incorrect because the conditions under which they would be shown false are never stated.

When evaluating any claim, ask: what would have to be true for this to be false? If no answer is available, the claim is operating outside the scientific framing. This doesn’t make it wrong; it makes it different in kind from scientific claims.

XI. Stereotyping and False Conjunctions

• Tendency to stereotype: The tendency to broadly generalise and categorise rather than look for specific nuance. Like the availability heuristic, this is generally a necessary trait for energy-saving in the brain. The categorisation lets us function; it also produces systematic distortions when categories are applied where they don’t fit.
• Failure to see false conjunctions: Most famously demonstrated by the Linda Problem (Kahneman and Tversky, 1983). Subjects were given a description of Linda as a young, single, philosophy-major woman engaged in social justice causes, then asked which was more probable:
  • Linda is a bank teller
  • Linda is a bank teller and an active feminist

Despite the second option necessarily being less probable (the intersection of two conditions is always less probable than either condition alone), most subjects rated the second as more probable. The vivid match between Linda’s profile and the “active feminist” descriptor overrode the logical constraint.

Vivid representations that match the perceived category beat logically prior facts about probability. This is the representativeness heuristic operating against base rate information.

XII. The Ignorance Problem

Continuing from Harari’s framing.

• The complexity overwhelm: If you feel overwhelmed and confused by the global predicament, you’re on the right track. Global processes have become too complicated for any single person to understand. How can you know the truth about the world and avoid falling victim to propaganda and misinformation?
  • Democracy was founded on the idea that the voter knows best. Free-market capitalism believes the customer is always right. Liberal education teaches students to think for themselves. It is a mistake to put too much trust into the rational individual. Most human decisions are based on emotions and heuristic shortcuts that worked well in the Stone Age but not in Silicon Valley.
• The myth of individuality: What gave humans the edge over other animals was the ability to operate in groups. We rely on the expertise of others for almost all daily tasks and yet we believe we know more than we really do. We have the illusion of knowledge but it works well for us. It is energy-efficient to not have to learn everything.
  • People hold strong views on many things that fall outside their expertise and rarely appreciate their ignorance. Most Americans who hold aggressive beliefs about the Middle East cannot find any of the relevant countries on a map. The power of groupthink is hard to dispel; you would sooner anger people with opposing facts than sway them. Most people don’t like to feel stupid, especially if it goes against a group ideology they belong to.
• Power distorts truth: With power, all problems appear to be overcome with it. Anybody who talks with you will have a conscious or unconscious agenda, so you can never have full faith in what they say. Great power acts like a black hole that warps everything around it. Revolutionary knowledge rarely makes its way to the centre because the centre is built on pre-existing knowledge. The periphery is filled with conspiracies and superstitious nonsense, which makes it very hard to distinguish between great ideas and great loads of nonsense. It takes too much time wading through it to find the gems; a person of power doesn’t have that luxury.
• The implication: Epistemic humility is not a virtue performance; it is the accurate response to actual conditions. You know less than you think you do about fewer topics than you think you have opinions on. This is the starting condition for mental model work, not the conclusion of it.

XIII. The Practical Bias Catalogue

Drawing on Andy Hunt’s Pragmatic Thinking and Learning. Practical software-engineering-adjacent treatment of cognitive biases.

• Anchoring: Just seeing a number affects how you predict or decide some quantity. By offering an example, you can prime someone’s perception on what something is worth.
• Fundamental attribution error: We ascribe other people’s behaviour to their personality instead of looking at the situation and context in which the behaviour occurs. We might excuse our own actions more easily. In reality, context is everything.
• Self-serving bias: The tendency to believe that if the project is a success, I’m responsible. If it failed, I’m not.
• Need for closure: We are not comfortable with doubt and uncertainty. We go to great lengths to resolve open issues. Resolving a problem early just masks it rather than solving it.
• Confirmation bias: Everyone looks for choice facts to fit their own preconceptions and theories.
• Exposure effect: We tend to prefer things because they are familiar.
• Hawthorne effect: People change their behaviour when they know they are being studied. Discipline is high; the excitement of something new fuels the effort. Eventually it wears off.
• False memory: It’s easy for your brain to confuse imagined events with real memories. We’re susceptible to the power of suggestion. Memory may be rewritten and changed with age, experience, worldview, focus.
• Symbolic reduction fallacy: Using quick symbolism to represent something complicated, which loses the nuances and truth.
• Nominal fallacy: Labelling a thing means you can explain it or understand it. A label is just that; naming it alone does not offer useful understanding.

How to overcome your biases.

• Do not discount unobserved or rare phenomena as impossible. Like discovering the existence of a black swan. Watch the outliers: “rarely” doesn’t mean “never.”
• Defer closure. Don’t fixate on a decision prematurely; you will reduce your options, perhaps to the point of eliminating the successful choice. Be comfortable with uncertainty.
• You don’t remember very well. Memory is unreliable and old memories change over time. The palest ink is better than the best memory.

XIV. Generational Archetypes

• The observation: Anything in the world when you’re born is normal and ordinary and part of how the world works. Anything invented between ages 15-35 is new and exciting and revolutionary and you can probably build a career in it. Anything after 35 is against the natural order of things.
• The biases driving you change over time: They will be different across generations. Some folks value job stability at the expense of abuse from their boss; others will leave at the slightest perceived offense. We tend not to wonder why we value the things we do. They could be instilled from parents, peers, or models. You are a product of your times.

Common generational tensions:

• Risk-taker vs risk-averse
• Individualism vs teamwork
• Stability vs freedom
• Family vs work

Four generational archetypes (Strauss and Howe framing)

• Prophet: Vision, values
• Nomad: Liberty, survival, honour
• Hero: Community, affluence
• Artist: Pluralism, expertise, due process

Archetypes produce opposing archetypes in the following generation. The pattern: Nomad produces X-er, Prophet produces Boomer, Artist produces Silent and Homeland, Hero produces GI and millennial.

• Calibration on the framework: The Strauss-Howe generational theory has value as orientation and limits as predictive social science. The four-archetype cycle pattern has been criticised for selection bias (it works when you cherry-pick examples and stops working at the edges) and for being unfalsifiable in some formulations. The reasonable position: useful as a way to notice that generations differ in patterned ways; not useful as a precise prediction framework. Engage with the broader observation; calibrate against the specific claims.
• Hedge your bets by embracing diversity: This prevents being pigeonholed and falling to your biases. Operating across generational cohorts produces broader perspective than operating only within your own.

XV. Myers Briggs

The Myers-Briggs Type Indicator categorises people into 16 types based on four binary dimensions. The framework is extensively used in business and self-help contexts. It has validity problems that warrant explicit naming.

The four dimensions (as MBTI presents them)

• Extraversion (E) vs Introversion (I): Inward or outward orientation. E energised by people and socialising; I territorial and needing private mental and environmental space.
• Sensing (S) vs Intuition (N): How you obtain information. S emphasises practicality and facts; N is imaginative, appreciates metaphor, and is innovative.
• Thinking (T) vs Feeling (F): How you make decisions. T based on rules; F evaluates personal and emotional impact alongside applicable rules.
• Judging (J) vs Perceiving (P): Decisions closed or open-ended. J uneasy until making a decision; P uneasy when making a decision.

The validity problems

• Poor test-retest reliability: People retaking the test even weeks apart often get different types. A test that classifies you as INTJ in March and ENFP in July is not measuring a stable trait.
• Poor predictive validity: MBTI types do not reliably predict job performance, relationship outcomes, or other measurable outcomes that the framework is often used to inform.
• The 16 types don’t reflect natural population clusters: Statistical analysis of MBTI dimensions shows they are continuous variables, not bimodal categories. The binary cutoffs are arbitrary. Most people who score “extravert” are actually near the middle of the continuum; they are not categorically different from people who score “introvert.”
• The four dimensions are not independent: Some correlate with each other in ways the framework treats as separate.
• The Big Five alternative: Modern personality psychology uses the Big Five model: Openness, Conscientiousness, Extraversion, Agreeableness, Neuroticism (OCEAN). The Big Five has better empirical support: high test-retest reliability, cross-cultural replication, predictive validity for life outcomes, and continuous measurement rather than arbitrary categorisation. If you want personality-trait orientation, Big Five is the better tool.
• The reasonable position on MBTI: Some people find the framework personally meaningful. The “types” can function as useful conversation starters. As an actual measure of personality, the framework is weaker than its popular adoption suggests. Treat it as folk psychology with limited validity; don’t make consequential decisions (hiring, partnership, career) on MBTI grounds. Use Big Five if you want a more empirically-supported framework.

XVI. Lizard Logic

A useful framing on the reactive patterns that activate when the system is dysregulated. Drawn from Andy Hunt’s treatment.

How to act like a lizard.

• Fight, flight, or fright: Fully aroused immediately. Ready to start swinging or run. If it is really bad, just freeze with fear.
• Get it now: Everything is immediate and automatic. Don’t think or plan; just follow your impulses and focus on excitement. Use sports metaphors a lot. Answer emails or surf the web instead of work.
• Be dominant: Claw and scratch to the leader of the pack so you can abuse everyone you know.
• Defend the territory: Never share info or space. Mark your territory and protect your interests. If someone does something without you, cry foul and demand to know why you weren’t included.
• If it hurts, hiss: Don’t fix the problem; spend your energy fixing the blame to someone else instead. Let everyone know it is not fair.
• Like me = good; not like me = bad: Your side is good and the other evil. Explain this to your teammates often.

“Lizard brain” is popular shorthand that simplifies the neuroscience. The amygdala-versus-prefrontal-cortex distinction is more nuanced than the reptilian-brain framing suggests. The “triune brain” model (reptilian-mammalian-human layers) that grounds lizard-brain talk is outdated in current neuroscience. Use the lizard logic framing as practical orientation toward recognising reactive patterns; don’t treat it as accurate neuroanatomy.

Practical observations.

Notice how long it takes you to get over your initial reaction to a perceived threat. How does your reaction change once you “think about it”?

Act on the impulse but not immediately. Plan for it; schedule it. Does it make sense later?

Write a new movie. If a given film keeps replaying in your head, sit down and craft a new one with a happy ending.

Smile. There’s evidence to suggest smiling can produce mood improvement (though the effect is modest and the dramatic claims in popular psychology about facial feedback warrant calibration).

XVII. Self-Verification Questions

The practical questions for catching yourself in motivated reasoning or unverified belief.

• On intuition: Trust intuition, but verify. If you believe your way intuitively feels better, great, but make sure it isn’t a cognitive bias at play first. Get some feedback, create a prototype, run some tests, chart some benchmarks. Prove the idea is good because your intuition may be wrong.
• On certainty: If you are dead solid convinced of something, ask yourself why. How do you know? Says who? Compared to whom?

The questions to apply to your own thinking:

• How do you know?
• Says who?
• How specifically?
• How does what I’m doing cause you to..?
• Compared to what or whom?
• Does it always happen? Can you think of an exception?
• What would happen if you did (or didn’t)?
• What stops you from…?

On measurement: Is there anything you can actually measure? Get hard numbers on? Any statistics? What happens when you talk this over with a colleague or someone with a very different perspective to you? Do they passively agree? Is that a danger sign? Do they violently oppose the idea? Does that give it credibility or not?

On definition: If you think you’ve defined something, try to define its opposite. This helps avoid the nominal fallacy. If all you have is a label, it’s hard to pin down its opposite in any detail. Contrast a behaviour, observation, or theory in detail. This gives you a deeper look at your definition with a more critical and attentive eye.

The Douglas Adams orientation

“The fact that we live at the bottom of a deep gravity well, on the surface of a gas-covered planet going around a nuclear fireball 90 million miles away and think this to be normal is obviously some indication of how skewed our perspective tends to be.” — Douglas Adams, The Salmon of Doubt

The conflict resolution synthesis: When in conflict, consider basic personality types, generational values, your own biases, others’ biases, the context, and the environment. Examine your own position carefully before assuming the conflict is the other person’s fault. Most conflicts have multiple cognitive biases operating on both sides simultaneously.

XVIII. Cross-Links

• Mental Models for the section overview
• Mental Model Basics for the System 2 tools that complement Heuristics Basics
• Brain 2.0 for externalising cognition through tools
• Mental Model Cheatsheet for the practical catalogue
• The Mental Model Rabbit Hole for the deeper material
• Resources for the reading list