Its job is not to win Nobel prizes and to pass math tests.

Its job is to get us to tomorrow.

It's a survival machine,

and it plays a lot of tricks with the facts

in order to get us to tomorrow.

That worked pretty well

when the risks were lions and tigers and bears

and the dark, oh, my.

It's not as good now when we need to rationalize

and reason and use the facts more

with the complicated risks we face in a modern age.

Climate change and genetically modified food

and unsustainable living on the planet,

that takes a lot more thinking.

We'd better accept that and understand it

so that we can apply that in order to avoid the pitfalls

of our subjective way of perceiving the world.

- It's quite a robust thinking system

that we've got between our ears, but what's going to happen,

and has been happening for several millennia now,

is we're gonna develop more and better-thinking tools,

and we're going to identify more weaknesses

in our rationality.

A weakness identified is

at least something that can be avoided to some degree.

We can learn workarounds.

We can recognize that we're suckers

for certain sorts of bad ideas

and, alerted to that, we can flag them when they come up.

- There's one way to be rational.

There are many ways to be irrational.

We could be irrational by getting confused,

not taking actions,

being myopic, vindictive, emotional, you name it.

There's lots of ways to be wrong,

and because of that, there's not one way

to fix it, but one interesting way

to try and inject some rationality is

to think from an outsider's perspective.

Here's what happens-

When you think about your own life,

you're trapped within your own perspective,

you're trapped within your own emotions

and feelings and so on, but if you give advice

to somebody else, all of a sudden, you're not trapped

within that emotional, combination, mishmash complexity,

and you can give advice that is more forward-looking

and not so specific to the emotions.

One idea is to basically ask people for advice.

So if you're falling in love with some person,

good advice is to go to your mother and say,

"Mother, what do you think about the long-term

"compatibility of that person?"

You're infatuated, right, when you're infatuated,

you're not able to see things three months down the road.

You're saying, "I'm infatuated.

"I'll stay infatuated forever, this will never go away."

Your mother, being an outsider, is not infatuated,

and she could probably look at things

like long-term compatibility and so on.

- We stick with a business plan or a career

or a relationship long after it's become quite clear

that it's not doing anything for us

or that it's actively destructive or self-destructive.

We have an irrational commitment

to whatever we have been doing

for a while, 'cause we don't like the idea

of our past investment having gone to waste

or because it's become part of our identity.

- Our brain is hardwired,

and the chemistry of the brain guarantees

that we feel first and think second.

That's initially when we encounter information,

but in an ongoing basis between the facts

and the feelings in our brain,

the feelings carry more weight.

They feel wonderful, but they might be wrong.

Recognizing that they might be wrong,

here's what you can do-

Take more time.

If the brain jumps to conclusions out of emotion first,

just assume that your first decision might not be

the most informed one.

Don't leap to conclusions.

Take more time, a half an hour, an hour, a day, two.

Think about it, cogitate on it, get more information.

Get more information, not just from sources

who already tell you what you know and believe,

because that's gonna reinforce what you know,

which will feel great but may not add to your knowledge.

Take more time and get more information,

and that allows that information

and the facts side of this dual system

to play more of a role.

- I'd like to introduce you

to a particularly powerful paradigm

for thinking, called Bayes' rule.

Bayes' rule is provably the best way

to think about evidence.

Many people, certainly including myself,

have this default way of approaching the world,

in which we have our pre-existing beliefs,

and we go through the world, and we pretty much stick

to our beliefs, unless we encounter evidence

that's so overwhelmingly inconsistent

with our beliefs about the world that it forces us

to change our mind and, you know, adopt a new theory

of how the world works,

and sometimes even then, we don't do it.

The implicit question that I'm asking myself,

that people ask themselves as they go through the world,

is, "When I see new evidence,

can this be explained with my theory?"

And if yes, then we stop there,

but after you've got some familiarity with Bayes' rule,

what you start doing is, instead of stopping

after asking yourself, "Can this evidence be explained

with my own pet theory?"

You also ask, "Would it be explained better

with some other theory,

or maybe just as well with some other theory?

Is this actually evidence for my theory?"

Bayes' rule is essentially a formalization

of the best way to reason about evidence,

the best way to change your mind

or update your confidence in your beliefs

when you encounter new information or have new experiences.

- I think that process of self-knowledge

and self-purification will continue to develop.

So it's not so much, although it might include,

the development of actual software technology

to help us think.

That's part of it, but also just the self-knowledge

that alerts us to foibles, blind spots in our own thinking.

- My fellow psychologists,

philosophers, neuroscientists often argue

that we're prisoners of the emotions,

that we're fundamentally and profoundly irrational,

and that reason plays very little role

in our everyday lives.

I honestly don't doubt that that's right in the short-term,

but I think in the long run, over time,

reason and rationality tends to win out.

I look at the world we're in now,

and for all of its many flaws and problems, I see signs

of those moral accomplishments all over the place.

We have a broader moral circle.

There's a lot of explanation for these changes,

but I think one key component has been exercise of reason,

and I'm optimistic we'll continue this in the future.