Skip to content

Bad Priors

5 min

This post was originally an email sent to the Better Questions Email List. For more like it, please sign up – it’s free.

“The map is not the territory.” Alfred Korzybski

Are you confused by the decisions people make?

I am.

Do you struggle to understand how, exactly people could believe what they believe?

Me too.

In the next couple emails, I’m going to try and hash this out.

(Don’t worry – I haven’t moved on from productivity. Just in research mode.)

Let’s start with statistics.

Now, if your eyesrolled into the back of your head – I get it.

I, too, spent my life believing I was “bad at math” and hating everything mathematical.

As I’ve grown older, I’ve become interested in picking up the mathematical mode of thinking

…if not the calculations, exactly.

When you try to learn math without actually doing any math problems, you get drawn to statistics.

Statistics – and statistical reasoning – are immediately applicable to life, so it’s fun!

(Trust me)

Let’s start today off with a statistical puzzle:

What percentage of American men are named Tom?

No googling, now.

It is unlikely you have any special insight into this problem…

(unless you work at the Census bureau…)

But I’d still like you to make a guess.

Go ahead – think of a number that sounds right to you.

Got it? OK – here’s the answer I got from Google:

A screenshot of Google that reads "99.78 percent of people with the first name Thomas are male."

(I know, I said no Googling, but it’s my newsletter and I’ll do what I want)

OK, so Google didn’t understand the question.

You may have got a cheap laugh out of that image, though.

Let me ask you another question:

How did you make your guess?

And how did you know the one in the image was wrong?

See, it’s rare for you to come to a question like with no information whatsoever.

Every single moment of your life, you are amassing a database of information about the world.

You estimate statistical likelihoods based on what you’ve experienced.

When I asked you to guess you considered how many Toms you know, or have heard of.

Then you did a rough calculation in your head – even if you were unaware of it.

That information you brought to the table – your beliefs about how many Toms there are – is a prior.

Your priors are all the information about the world that you bring to any decision making process…

What you believe before you see any specific evidence.

You consult that information before you make a prediction.

And of course, all decisions are just predictions about how things will turn out.

Your priors influence what you predict AND how you interpret evidence afterwards.

As Jordan Ellenberg points out in How Not To Be Wrong:

“If an experiment provided statistically significant evidence that a new tweak of an existing drug slowed the growth of certain kinds of cancer, you’d probably be pretty confident the new drug was actually effective.

But if you got the exact same results by putting patients inside a plastic replica of Stonehenge, would you grudgingly accept that the ancient formations were actually focusing vibrational earth energy on the body and stunning the tumors? You would not, because that’s nutty. You’d think Stonehenge probably got lucky.

You have different priors about those two theories, and as a result you interpret the evidence differently, despite it being numerically the same.”

Our priors are essential to how we understand the world.

So the real question is:

How good are my priors?

To answer that question, we counter with another…

(Have you noticed that’s a theme with these fucking emails? Jesus, Dan)

How representative of the world around me are my experiences?

An important thing to note about priors is that they rarely spring forth from nothing. They’re based on how we experience the world.

If 50% of the men you meet are Toms, you’d be likely to extrapolate something from that.

In fact, you’d be silly not to.

But if you live in Tomsville, state capital of West Tomsginia – a state where the name Tom is 10x as common as everywhere else – that prior knowledge of Toms can lead you astray when predicting how many Toms are in the world…

Even though it’s based on lived experience.

This is the rub: our priors can be both real and inaccurate.

Take our perception of crime.

We over-estimate how likely we are to fall victim to crime, despite national violent crime rates dropping for more than a decade.

Why is this? As Brian Christian and Tom Griffiths write in Algorithms to Live By:

…the representation of events in the media does not track their frequency in the world. As sociologist Barry Glassner notes, the murder rate in the United States declined by 20% over the course of the 1990s, yet during that time period the presence of gun violence on American news increased by 600%.

And this is from someone who has strongly defended the news media.

When you talk with friends, you tend to talk about what’s most interesting, what will make a cool or fun story.

We rarely talk about what’s representative, which leads to a skewed sense of what other people experience.

Or your Instagram feed – what gets deemed worthy of getting posted to the ‘gram?

It isn’t daily occurrences, it isn’t everyday moments – it’s what stands out, what’s special.

A non-stop scroll of everyone’s special moments can make those moments seem more common than they are.

Our personal reality is like glimpsing a forest through a keyhole:

True, in the sense that it depicts reality…

But misleading in the sense that it represents only a fraction of a fraction of the whole.

All this makes it very, very difficult to maintain accurate priors.

And that brings us back to our friend Korzybski, quoted at the beginning of this essay.

“The map is not the territory.”

Reality is far too vast for us to comprehend. It’s too much data.

But we can’t give up – we have to make our way through the world.

So we use our priors as a map.

Maps help us predict what’s next – help us find our way through the landscape.

But if our map is wrong – if our priors are wrong – we end up in the wrong place.

This, by the way, is how we get to broad empathy for people, no matter how wrong-headed they may be:

Their priors are wrong….

And so are ours.

It’s just a question of how wrong.

Next week, I’ll expand a bit on this map and territory stuff. The week after, we’ll talk about how you actually apply this…

– to make more money

– to be more successful

– to avoid complete disaster.

Just so you know this is actually going somewhere.


Subscribe to receive the latest posts in your inbox.