The Bias Map: 12 Tricks Your Own Brain Plays on You

In the previous article (You Don't Believe It Because It's True. You Believe It Because It's Familiar.) I explored two biases in more depth: confirmation bias and the illusory truth effect. I felt it was important (partly for my own sake) to have a longer piece on this, something I can peek at myself.

So here's the complete(r) list for you too. Not so you memorize all twelve word for word - but so you have a map you can look back at when something seems suspiciously simple or suspiciously confident.

Biases in decision-making

Anchoring - the anchor effect

When a completely random first number (a starting price, an estimate, even a totally irrelevant number) influences what you think second - even if you know the first number means nothing. Tversky and Kahneman's 1974 paper, already cited in the previous article, was the first to describe it: our brain uses the first number it gets as an “anchor”, and adjusts every subsequent estimate to it, not to reality.

(If you've ever haggled over something, and the seller deliberately started far too high - now you know exactly what they were doing.)

Availability heuristic - what comes to mind seems more common

Tversky and Kahneman's 1973 paper showed that we don't consider something probable because it's actually common - but because it comes to mind easily. If you recently heard about a plane crash, flying suddenly feels more dangerous, even though statistically nothing has changed. Media coverage isn't the same as actual risk, but our brain happily blurs the two together.

Status quo and loss aversion - why losing is harder than winning

Kahneman and Tversky's 1979 prospect theory, which later earned a Nobel Prize, showed that a loss hurts emotionally roughly twice as much as an equal gain feels good. This isn't logical - mathematically it's the same amount - yet it's one of the strongest, most consistent patterns ever measured in human decision-making. It's why we cling to things (a job, a relationship, an investment) that deep down we know are no longer good for us.

Sunk cost fallacy - “I've put so much in already, I can't quit now”

Arkes and Blumer's classic 1985 paper named the pattern where, because of time, money or energy already spent, we keep going with something that, from this moment on, isn't worth it from any rational point of view. The resource already spent is in the past. No future decision of yours can bring it back - all that matters is what happens if you move on now.

Hindsight bias - “I knew it all along”

According to Fischhoff's 1975 experiment, as soon as we learn the outcome of an event, our brain retroactively edits our memories as if it had always been obvious. That's why almost everyone “knew in advance” that a relationship would end, or a company would go under - they just never said so before it happened.

Biases in how we see ourselves

Dunning-Kruger effect - when ignorance breeds confidence

Kruger and Dunning's 1999 paper found that the less someone knows about a field, the worse they are at judging the limits of their own knowledge - and so they often overestimate themselves. (The other half of the research is less well known but at least as important: truly skilled people tend to underestimate themselves, because for them it's not even a question how much they still don't know.)

Optimism bias - “it won't happen to me”

Weinstein's 1980 research showed that we systematically underestimate our own chances of bad things (illness, accidents, divorce) while overestimating good things (success, long life). This isn't stupidity - in fact it demonstrably helps us function in an uncertain world - but that's exactly why it's hard to shake, and exactly why it's worth knowing it's there.

Negativity bias - the bad is louder

According to the influential 2001 review by Baumeister and colleagues, our brain gives disproportionately more weight to negative information than to positive - one criticism stings longer than five compliments feel good. This makes evolutionary sense (noticing danger matters more than noticing joy), but it's also why a news broadcast is full of catastrophe while the world is improving on plenty of measurable indicators.

Social biases

Halo effect - when one trait “colors” all the others

Nisbett and Wilson's 1977 experiment showed that if we have one positive impression of someone (attractive, pleasant voice, well-dressed), we tend to project it onto their completely unrelated traits too - we consider them smarter, more trustworthy, more competent, without any actual evidence. That's why a confident delivery seems credible all by itself - regardless of the content.

Bandwagon effect / social proof - if everyone's doing it, it must be good

Solomon Asch's 1951 conformity experiments, classics by now, showed that people tend to give an obviously wrong answer just because the group around them said so. We don't even necessarily consciously believe the majority's opinion - we simply don't dare stand out against it. This mechanism is also behind why a product, news item or opinion seems more credible because “many people share it” - regardless of whether that makes it true.

The ones we've already covered

Confirmation bias

I wrote about this at more length in the previous article: we tend to search for and interpret information in a way that confirms what we already believe. According to Nickerson's 1998 overview, it isn't a single phenomenon but “a ubiquitous phenomenon in many guises”.

Illusory truth effect

Also from the previous article: the more times you hear a statement, the truer it feels - completely regardless of whether it's actually true. We've known this since Hasher, Goldstein and Toppino's 1977 experiment, and Fazio and colleagues showed in 2015 that even your own correct prior knowledge doesn't protect you from it.

What this map is for

Not for stopping every single thought and asking: “which bias is this now?” That would be exhausting, and that's not the point.

It's for this: when something triggers an unusually strong emotional reaction in you - instant reassurance, instant outrage, an instant “everybody knows that” feeling - you have a moment to stop and ask:

did the content convince me, or the way it arrived?

This is exactly what the Interpretation Firewall is about. The goal isn't to weed out your own biases completely - they're one of the cornerstones of being human, and, from a survival standpoint, important ones, and nobody is an exception (not even the one who teaches this for a living, right?). The goal is that next time you have a map you can look back at, and catch your cognitive autopilot in the act, if it happens to want to fly you in a completely different direction from what's good for you.

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Sources

• Amos Tversky, Daniel Kahneman: Judgment under Uncertainty: Heuristics and Biases, Science, 1974. (anchoring)
• Amos Tversky, Daniel Kahneman: Availability: A Heuristic for Judging Frequency and Probability, Cognitive Psychology, 1973.
• Daniel Kahneman, Amos Tversky: Prospect Theory: An Analysis of Decision under Risk, Econometrica, 1979.
• Hal R. Arkes, Catherine Blumer: The Psychology of Sunk Cost, Organizational Behavior and Human Decision Processes, 1985.
• Baruch Fischhoff: Hindsight Is Not Equal to Foresight: The Effect of Outcome Knowledge on Judgment under Uncertainty, Journal of Experimental Psychology: Human Perception and Performance, 1975.
• Justin Kruger, David Dunning: Unskilled and Unaware of It, Journal of Personality and Social Psychology, 1999.
• Neil D. Weinstein: Unrealistic Optimism About Future Life Events, Journal of Personality and Social Psychology, 1980.
• Roy F. Baumeister, Ellen Bratslavsky, Catrin Finkenauer, Kathleen D. Vohs: Bad Is Stronger Than Good, Review of General Psychology, 2001.
• Richard E. Nisbett, Timothy D. Wilson: The Halo Effect: Evidence for Unconscious Alteration of Judgments, Journal of Personality and Social Psychology, 1977.
• Solomon E. Asch: Effects of Group Pressure upon the Modification and Distortion of Judgments, in Groups, Leadership and Men (ed. H. Guetzkow), 1951.
• Raymond S. Nickerson: Confirmation Bias: A Ubiquitous Phenomenon in Many Guises, Review of General Psychology, 1998.
• Lynn Hasher, David Goldstein, Thomas Toppino: Frequency and the Conference of Referential Validity, Journal of Verbal Learning and Verbal Behavior, 1977.
• Lisa K. Fazio, Nadia M. Brashier, B. Keith Payne, Elizabeth J. Marsh: Knowledge Does Not Protect Against Illusory Truth, Journal of Experimental Psychology: General, 2015.