How to catch the moments that need slow thinking, test a belief against its best counter-evidence, resist an anchor, run a pre-mortem and get out of sunk costs, with the exact protocols, what to do when a check fails, and how to measure your progress.
Doctor's Note: These checks are for everyday choices. If worst-case thinking, constant worry or harsh self-judgment fills your days or stops you from deciding at all, talk to a doctor or therapist. If you ever feel unsafe or think about harming yourself, find a free crisis line in your country at findahelpline.com (988 in Canada and the US), or call your local emergency number now.
Here's What's Actually Going On in Your Head
Try this before you read on. A bat and a ball cost 1.10 in total. The bat costs 1.00 more than the ball. How much is the ball? Most people answer "10 cents", because 1.10 splits so neatly into 1 and 10 cents. The right answer is 5 cents, since 0.05 plus 1.05 makes 1.10 [5].
The World Bank's report on mind and behaviour explains why. Your mind has a quick, automatic way of thinking and a slow, deliberate one. The quick one hands you a plausible answer before the slow one has time to check it [5]. Most of the time this saves you effort and works well. Most of the frames your quick mind uses are useful, and you could not get through a day without some mental shortcuts [5]. The trouble starts when the shortcut meets a choice it was not built for: a big price, a heated argument, a plan you are attached to.
Being clever does not protect you. When World Bank staff read the same data table, they were less accurate when it was framed as minimum wage laws and poverty than when it was framed as a skin cream, and their ability and seniority did not explain the gap [5]. Strain makes it worse. Sugar cane farmers in India scored lower on thinking tests just before harvest, when money was tight, than just after. The gap was about three quarters of the effect of losing a full night's sleep [5].
So the aim of this guide is not to memorise a list of biases. It is to build five checks you run at the right moments. Training that has people practise checks works better than reading about them: a single training session made graduate students 19% less likely to pick a solution that only confirmed their first guess, on a surprise business case with no reminder of bias [6]. Lasting effects need practice: in a review of bias training, only 12 studies tested whether gains lasted 14 days or more, and most of those used practice games, which beat videos [7].
Step 1: Catch the Moments That Need Slow Thinking and Take 10 Seconds
WHY THIS MATTERS
You cannot slow down for every choice, and you do not need to. The quick mind is fine for lunch. It fails most when it hands you an answer before the slow mind can check it, as in the bat and ball [5]. Time pressure, poverty and money stress all make it harder for the slow mind to step in [5]. So the skill is to spot the few moments that need a check, then give them 10 seconds.
- Learn the three signals by heart: high stakes (money, health, a relationship, a job, anything hard to undo), strong feelings (angry, scared, excited, desperate to be right) and an answer that came too easily (it "just feels obvious").
- When one signal fires, stop for 10 seconds before you say yes, buy, send or commit.
- In those 10 seconds, ask one question: "Why might my first answer be wrong?" Name one reason, even a weak one.
- If you are under time pressure or money stress, treat that as an extra signal, because strain makes the slow mind harder to switch on [5]. Move the choice to a calmer hour if you can.
- If someone pushes you to decide now, say: "I don't make decisions this size on the spot. I'll get back to you." A fair offer will still be there.
How the 10-second check works in practice
Example: a salesperson offers a phone plan "only for today". Signals: money (high stakes) and excitement. Ten seconds: "Why might yes be wrong? I have not compared any other plan." You say you will decide tomorrow. The check did its job by giving the slow mind a turn.
When it does not work
- You only notice the signal afterwards. That is normal at first. Write the missed moment down that evening and name the signal you missed. Most people miss the same one again and again, so this tells you which signal to watch hardest.
- You freeze and cannot decide at all. The check is 10 seconds, not 10 days. If a small choice still feels impossible, take the first answer. If this happens often, see the Doctor's Note.
- Everything feels high stakes. Keep a short list of the choices that really count for you this month (a job, a big buy, a move) and run the check only for those.
Special groups
If you are going through money stress, a tough exam period, a new baby or long shifts, your slow mind has less to spare [5]. Make fewer big decisions during those weeks, and put them at the start of the day or after a rest day if you can.
Within 2 weeks you catch at least one signal before you act, not after, and you notice which of the three signals you miss most.
Step 2: Test a Belief: Search the Best Evidence Against It and Ask the Mirror Question
WHY THIS MATTERS
Once you hold a view, you read new evidence in its favour. In a classic set of experiments, people judged new evidence on social issues in a biased way, and the fix that worked best was getting them to consider the opposite: to bring to mind the possibilities at odds with what they already believed [2]. Being told only to "be as fair and unbiased as possible" worked less well [2]. Good intentions are not enough; you need a concrete question.
- Pick the belief you are about to act on: a diet, an investment, a claim about a person or a group, a news story.
- Search for the strongest case against it, in neutral words. Type "evidence against [topic]" or "[topic] pros and cons", never "why [topic] works".
- Read the best one or two pieces you find, not the weakest. Look for official bodies or research, not opinion posts.
- For each piece of evidence, on either side, ask the mirror question: "Would I accept this evidence if it pointed the other way?" If the answer is no, give it less weight, whichever side it supports.
- Write one sentence: "The best argument against my view is ___." If you cannot write it, you have not finished the check.
- Decide what would change your mind before you look further: "If I find ___, I will change my view."
The mirror question in practice
Example: you believe a supplement works because a friend felt better. Mirror: "If my friend had felt worse, would I take that as proof it does harm?" Probably not. So one friend's story counts for little, on both sides.
When it does not work
- You find only evidence for your view. Check your search words. Words like "benefits" or "why" pull in one side only.
- You feel angry reading the other side. That is the strong-feelings signal from Step 1. Stop, come back after a break, and read only the summary first.
- The topic is tied to who you are (politics, religion, your job). This is where bias is strongest: in the World Bank test, staff read data less accurately on a topic tied to their views than on a neutral one [5]. Ask someone you trust who disagrees with you to give you their best argument, and listen without replying for 2 minutes.
Special groups
Experts are not immune. Professional staff were less accurate on a topic tied to their field's debates, whatever their ability or seniority [5]. The more you know about a topic, the more you need this step.
Within 3 weeks you can write down the best argument against at least one belief you hold, and you have softened or changed at least one view.
Step 3: Resist an Anchor: Write Your Own Number Before You See Theirs
WHY THIS MATTERS
An anchor is a number that should not matter but still pulls your judgment towards it [5]. Experienced judges and lawyers gave longer sentences after hearing a high number, even when the number came from a roll of rigged dice [5]. When people had 5 seconds to estimate 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8, the median guess was 512; when the same numbers came in reverse order, starting with 8, it was 2,250. The real answer is 40,320 [5]. Two defences work. First, have your own number ready, so theirs is not the first one in your head. Second, when theirs comes first anyway, list reasons it is wrong: this "consider the opposite" step reduced the anchor's effect, including for experts in a real-world setting [3].
- Before you see a price, offer, quote, salary or estimate, write your own number on paper or in your phone.
- Under it, write one line on how you got it: two or three real prices you checked, your budget, or your walk-away point.
- Write your walk-away number too: the point where you say no.
- When their number comes first anyway (a list price, a "was 199" sticker, a first offer), write 2 reasons it could be too high or too low before you reply [3].
- Answer from your own number, not from theirs. If theirs is far from yours, say: "That's not what I found. I was looking at ___."
When it does not work
- You have no idea what a fair number is. Then you are not ready to answer. Take a day, check 3 comparable prices, and come back.
- You wrote a number, but theirs still feels "right". That feeling is the anchor at work [3]. Read your one line of reasons out loud, then go through the 2 reasons theirs could be wrong.
- The anchor came from you. Your first guess anchors you too. Before you settle on an estimate, write one number well above it and one well below it, and ask why each could be right.
Special groups
When you are short of money, quick choices about loans and prices are where the anchor costs most, and strain makes slow thinking harder [5]. Write your number at home, before the shop or the call.
In your next 5 purchases, offers or estimates, at least 3 start from a number you wrote first.
Step 4: Run a Pre-Mortem: Imagine It Failed a Year From Now, Then Fix the Top Risks
WHY THIS MATTERS
Once you commit to a plan, it is hard to see its weak spots, and people in a group often keep their doubts to themselves. A pre-mortem flips the question. You imagine the plan has already failed and work out why, then change the plan to deal with those causes [4]. In a study comparing it with ordinary brainstorming, teams using the pre-mortem found better quality risks, made more useful changes to the plan and spotted more rare, high-impact risks [4].
- Before a big plan (a move, a launch, a wedding, a new business, a training programme), say: "It is one year from now. This plan failed. What went wrong?"
- Everyone writes reasons alone first, for 5 minutes, before anyone speaks. On your own, write for 5 minutes without stopping.
- Share one reason at a time, going round, until all are on one page.
- Pick the top 2 by how likely and how costly they are.
- Change one thing in the plan for each of the top 2: a backup supplier, a savings buffer, a second person who can step in, a test run first.
- Write one early warning sign for each top risk. Then go to Step 5 and set a stopping rule.
When it does not work
- Nobody wants to say anything negative. Make it a game: whoever finds the most likely failure wins.
- The list is too long to act on. Keep only the top 2. A plan with 2 real fixes beats a list of 20 worries.
- Everyone lists the same safe risks. Ask: "What is the strange, unlikely way this could fail badly?" Rare, high-impact risks are exactly what the pre-mortem is good at finding [4].
Special groups
Families and couples can run a pre-mortem on a move or a big purchase. Ask children or teens for their reasons first, so the adults' views do not set the list.
Your next big plan starts with 2 fixes already in place and one warning sign for each.
Step 5: Get Out of Sunk Costs: "Would I Choose It Today?" and a Stopping Rule Set in Advance
WHY THIS MATTERS
Sunk cost bias is the pull to keep going with something because you have already put money, time or effort into it [5]. It is real and well measured: a meta-analysis of 98 effect sizes found clear evidence of it in money decisions [8]. When World Bank staff were asked about a failing project, the more of its money had already been spent, the more likely they were to keep funding it [5]. Stopping feels like admitting waste, but carrying on can waste even more [5]. The World Bank's advice is to make it easy to justify stopping: set criteria for ending a project that are clear and public, and remove the penalty for stopping [5].
- For anything you keep doing mainly because you started (a course, a renovation, a car, a business idea, a subscription), ask: "If I didn't have this, would I choose it today, at today's price?"
- If the answer is no, list what you would do with the time or money instead. That is the real choice in front of you.
- Before you start any new big commitment, write a stopping rule with a date and a number: "If by [date] I have not reached [result], or I have spent more than [amount], I stop or rethink."
- Tell one person your rule, or write it where others will see it. Public criteria make stopping easier [5].
- On the date, judge by the rule, not by what you have already spent.
- If you stop, write one line on what you learned. That turns the "waste" into something you can justify, which makes the next stop easier [5].
When it does not work
- You keep moving the stopping date. Set the rule with someone else and agree that only the two of you together can change it.
- You feel you must use what you paid for (a ticket, a gym pass, a meal). The pull of a past payment on using things fades with time [8]. If you can wait a day, the right choice is often clearer.
- Others expect you to finish. Staff judged their colleagues as even more likely to keep funding a failing project than themselves, a sign of a shared habit of not stopping [5]. Say it out loud: "If we were starting today, would we choose this?"
Special groups
Younger adults fell for sunk costs more often than older adults [8], so students and young workers have the most to gain from writing stopping rules for courses, jobs and projects.
Every new big commitment this month has a written stopping rule with a date, and you have dropped or changed at least one thing you kept only because you had started.
Step 6: Track Your Five Checks for 60 Days
WHY THIS MATTERS
Gains from bias training only count if they last and carry over to real choices, and few studies have tested this [7]. The trainings that lasted were practice-based, such as games with feedback, and they beat watching a video [7]. Your own real choices are your practice ground.
- Keep a decision-check tally for 60 days in a notebook or phone note. For each big choice or plan, write one line: the date, the choice, which of the 5 checks you used (10-second pause, mirror question, your number first, pre-mortem, stopping rule) and whether it changed anything.
- On day 7, count the choices you checked and how many changed. Do it again on day 30 and day 60.
- Aim for 20 or more big choices checked over 60 days, with at least 5 where a check changed your decision or plan.
- Once a month, read back your tally and circle the check you skip most. Practise that one first next month.
- Every 3 months, rate yourself on the Skill Check table below.
By day 60 you use at least one check on most big choices without needing to remind yourself, and you can point to 5 choices that came out better.
Conclusion
You will never switch biases off. The quick mind is part of how everyone thinks [5]. What you can change is when the slow mind gets its turn. Five checks cover the costly moments: pause on the three signals, test your belief with the mirror question, write your number first, run a pre-mortem, and set a stopping rule. Start with Step 1 this week. It needs no extra time.
Myths
Myth 1: "If I know the names of the biases, I won't fall for them."
Knowing helps only a little. Teaching students about biases gave a small effect, and it is unclear whether it reaches real-life decisions [1]. Practising checks on real problems works better [6].
Myth 2: "Smart, experienced people are less biased."
Professional World Bank staff read the same data less accurately when the topic touched their views, and ability and seniority did not explain it [5]. Experienced judges were pulled by numbers from rigged dice [5].
Myth 3: "Just trying to be fair is enough."
People told to be fair and unbiased corrected less than people told to consider the opposite [2]. A specific question beats good intentions.
Myth 4: "Quitting means everything I put in was wasted."
What is spent is spent either way. Carrying on with a failing plan can waste more [5]. Write down what you learned, and stopping becomes something you can justify [5].
FAQ
Do I need to run all five checks on every choice?
No. Run the 10-second check in Step 1 when a signal fires. Use the others when they fit: the mirror question for beliefs, your number first for prices, a pre-mortem and a stopping rule for big plans.
How long before this works?
A single training session reduced confirmation bias on a later surprise case with no reminder [6]. Lasting change needs repeated practice [7], so give the tally 60 days.
What if the other side's number really is fair?
Then your own research will show it, and you lose nothing. The aim is that your answer comes from your reasons, not from whichever number you heard first [3].
Is a pre-mortem just being negative?
No. You look for failures in order to fix them before you start, and teams that did this found better risks and made more useful changes than brainstorming teams [4].
Do sunk costs affect everyone the same way?
No. Younger adults fell for them more often than older adults, and the pull to use something you paid for faded with time [8].
Skill Check
| Skill | Starting | Solid | Strong |
|---|---|---|---|
| Slow down in time: of your last 5 high-stakes or emotional choices, how many had the 10-second pause before you decided? | 0 or 1 of 5 | 3 of 5 | 5 of 5 |
| Consider the opposite: in the last month, how many strong beliefs did you test against the best evidence against them? | None | 2 | 4 or more, and you changed or softened at least one |
| Your own number first: in your last 5 purchases, offers or estimates, how many started from a number you wrote first? | 0 or 1 of 5 | 3 of 5 | 5 of 5 |
| Pre-mortem: of your last 3 big plans, how many had a pre-mortem with 2 fixes? | 0 | 2 of 3 | 3 of 3 |
| Stopping rules: of your last 3 big commitments, how many had a written stopping rule with a date? | 0 | 2 of 3 | 3 of 3, and you acted on at least one rule |
What Next
- Start your 60-day decision-check tally today and run the 10-second check on the next choice where a signal fires.
- At day 30, pick the check you skip most and practise it on purpose.
- When you want more tools, use the Go further list below.
Go further
- Fast Mind, Slow Mind and Your Bias Blind Spot: Why You See Others' Biases First: why you spot others' biases first.
- Catch Biases Before They Cost You: A Decision Checklist, Real Dissent, a Bias Log and an 8-Week Plan: a fuller checklist and bias log.
- Why You Self-sabotage, and How to Catch It Before It Costs You: the pre-mortem in more depth.
- When to Trust Your Gut: Test Your Intuition Against Outcomes and Train It: when the quick mind is worth trusting.
- Stop Waiting for Certainty: Decide Without All the Answers and Count the Cost of Not Deciding: for when checks turn into stalling.
- Trust Your Own Judgement Again: End Self-doubt and Self-gaslighting: if doubting yourself is the bigger problem.
