RailsConf 2014 - Cognitive Shortcuts: Models, Visualizations, Metaphors, and Other Lies

SAM LIVINGSTON-GRAY: Hello. Welcome to the
very

last session of RailsConf.

When I leave this stage,

they are gonna burn it down.

AUDIENCE: Yeah!

S.L.: I have a couple of items of business

before I launch into my presentation proper.
The first

of which is turning on my clicker. I work

for LivingSocial. We are hiring. If this fact
is

intriguing to you, please feel free to come
and

talk to me afterwards. Also, our recruiters
brought a

ton of little squishy stress balls that are
shaped

like little brains. As far as I know, this

was a coincidence, but I love the tie-in so

I brought the whole bag. I had them leave

it for me. So if you would like an

extra brain, please come talk to me after
the

show.

A quick note about accessibility. If you have
any

trouble seeing my slides, hearing my voice,
or following

my weird trains of thought, or maybe you just

like spoilers, you can get a PDF with both

my slides and my script at this url. It's

tinyurl dot com, cog dash shorts dash railsconf.
I

also have it up here on a thumb drive,

so if the conference wi-fi does what it usually

does, please go see Evan Light up in the

second row.

I'm gonna leave this up for a couple more

minutes. And I also want to give a shoutout

to the opportunity scholarship program here.
To quote the

RailsConf site, this program is for people
who wouldn't

usually take part in our community or who
might

just want a friendly face during their first
time

at RailsConf. I'm a huge fan of this program.

I think it's a great way to welcome new

people and new voices into our community.
This is

the second year that I've volunteered as a
guide

and this is the second year that I've met

somebody with a fascinating story to tell.
If you're

a seasoned conference veteran, I strongly
encourage you to

apply next year.

OK. Programming is hard. It's not quantum
physics. But

neither is it falling off a log. And if

I had to pick just one word to explain

why programming is hard, that word would be
abstract.

I asked Google to define abstract, and here's
what

it said.

Existing in thought or as an idea, but not

having a physical or concrete existence.

I usually prefer defining things in terms
of what

they are, but in this case I find the

negative definition extremely telling. Abstract
things are hard for

us to think about precisely because they don't
have

a physical or a concrete existence, and that's
what

our brains are wired for.

Now, I normally prefer the kind of talk where

the speaker just launches right in and forces
me

to keep up, but this is a complex idea,

and it's the last talk of the last day,

and I'm sure you're all as fried as I

am. So, here's a little background. I got
the

idea for this talk when I was listening to

the Ruby Rogues podcast episode with Glenn
Vanderburg. This

is lightly edited for length, but in that
episode,

Glenn said, The best programmers I know all
have

some good techniques for conceptualizing or
modeling the programs

that they work with. And it tends to be

sort of a spatial/visual model, but not always.
And

he says, What's going on is our brains are

geared towards the physical world and dealing
with our

senses and integrating that sensory input.

But the work we do as programmers is all

abstract. And it makes perfect sense that
you would

want to find techniques to rope the physical
sensory

parts of your brain into this task of dealing

with abstractions. And this is the part that
really

got my attention. He says, But we don't ever

teach anybody how to do that or even that

they should do that.

When I heard this, I started thinking about
the

times that I've stumbled across some technique
for doing

something like this, and I've been really
excited to

find a way of translating a programming problem
into

some form that my brain could really get a

handle on. And I was like yeah, yeah, brains

are awesome. And we should be teaching people
that

this is a thing they can do.

And I thought about it, and some time later,

I was like, wait a minute. No. Brains are

horrible. And teaching people these tricks
would be totally

irresponsible, if we also didn't warn them
about cognitive

bias. I get to that in a little bit.

This is a talk in three parts. Part one,

brains are awesome. And as Glenn said, you
can

rope the physical and sensory parts of your
brain

as well as a few others I'll talk about

into helping you deal with abstractions. Part
two, brains

are horrible and they lie to us all the

time. But if you're on the look out for

the kinds of lies that your brain will tell

you, in part three I have an example of

the kind of amazing hack that you just might

be able to come up with.

Our brains are extremely well-adapted for
dealing with the

physical world. Our hindbrains, which regular
respiration, temperature, and

balance, have been around for half a billion
years

or so. But when I write software, I am

leaning hard on parts of the brain that are

relatively new in evolutionary terms, and
I'm using some

relatively expensive resources.

So over the years I have built up a

small collection of techniques and shortcuts
that engage specialized

structures of my brain to help me reason about

programming problems. Here's the list.

I'm gonna start with a category of visual
tools

that let us leverage our spatial understanding
of the

world and our spatial reasoning skills to
discover relationships

between different parts of a model. Or just
to

stay oriented when we're trying to reason
through a

complex problem.

I'm just gonna list out a few examples of

this category quickly, because I think most
developers are

likely to encounter these, either in school
or on

the job. And they all have the same basic

shape. They're boxes and arrows.

There's Entity-Relationship Diagrams, which
help us understand how our

data is modeled. We use diagrams to describe
data

structures like binary trees, linked lists,
and so on.

And for state machines of any complexity,
diagrams are

often the only way to make any sense of

them. I could go on, but like I said,

most of us are probably used to using these,

at least occasionally.

There are three things that I like about these

tools. First, they lend themselves really
well to standing

up in front of a white board, possibly with

a co-worker, and just standing up and moving
around

a little bit will help get the blood flowing

and, and get your brain perked up.

Second, diagrams help us offload some of the
work

of keeping track of things, of different concepts,
by

attaching those concepts to objects in a two-dimensional
space.

And our brains have a lot of hardware support

for keeping track of where things are in space.

And third, our brains are really good at pattern

recognition, so visualizing our designs can
give us a

chance to spot certain kinds of problems just
by

looking at their shapes before we ever start
typing

code in an editor, and I think that's pretty

cool.

Here's another technique that makes use of
our spatial

perception skills, and if you saw Sandi's
talk yesterday,

you'll know this one. It's the squint test.
It's

very straight forward. You open up some code
and

you either squint your eyes at it or you

decrease the font size. The point is to look

past the words and check out the shape of

the code.

This is a pathological example that I used
in

a refactoring talk last year. You can use
this

technique as an aid to navigation, as a way

of zeroing in on high-risk areas of code,
or

just plain to get oriented in a new code

base. There are a few specific patterns that
you

can look for, and you'll find others as you,

as you do more of it.

Is the left margin ragged, as it is here?

Are there any ridiculously long lines? There's
one towards

the bottom. What does your syntax highlighting
tell you?

Are there groups of colors or are colors sort

of spread out? And there's a lot of information

you can glean from this. Incidentally, I have
only

ever met one blind programmer, and we didn't
really

talk about this stuff. If any of you have

found that a physical or a cognitive disability
gives

you a, an interesting way of looking at code,

or understanding code I suppose, please come
talk to

me, because I'd love to hear your story.

Next up, I have a couple of techniques that

involve a clever use of language. The first
one

is deceptively simple, but it does require
a prop.

Doesn't have to be that big. You can totally

get away with using the souvenir edition.
This is

my daughter's duck cow bath toy. What you
do

is you keep a rubber duck on your desk.

When you get stuck, you put the rubber deck

on top- rubber duck, excuse me, on top of

your keyboard, and you explain your problem
out loud

to the duck.

[laughter]

Really. I mean, it sounds absurd, right. But
there's

a good chance that in the process of putting

your problem into words, you'll discover that
there's an

incorrect assumption that you've been making
or you'll think

of some other possible solution.

I've also heard of people using teddy bears
or

other stuffed animals. And one of my co-workers
told

me that she learned this as the pet-rock technique.

This was a thing in the seventies. And also

that she finds it useful to compose an email

describing the problem. So for those of you
who,

like me, think better when you're typing or
writing

than when you're speaking, that can be a nice,

a nice alternative.

The other linguistic hack that I got, I got

from Sandi Metz, and in this book, Practical
Oriented

Design in Ruby, PODR for short, she describes
a

technique that she uses to figure out which
object

a method should belong. I tried paraphrasing
this, but

honestly Sandi did a much better job than
I

would, describing it, so I'm just gonna read
it

verbatim.

She says, How can you determine if a Gear

class contains behavior that belongs somewhere
else? One way

is to pretend that it's sentient and to interrogate

it. If you rephrase every one of its methods

as a question, asking the question ought to
make

sense.

For example, "Please Mr. Gear, what is your
ratio?"

seems perfectly reasonable, while "Please
Mr. Gear, what are

your gear_inches?" is on shaky ground, and
"Please Mr.

Gear, what is your tire(size)?" is just downright
ridiculous.

This is a great way to evaluate objects in

light of the single responsibility principle.
Now I'll come

back to that thought in just a minute, but

first, I described the rubber duck and Please,
Mr.

Gear? as techniques to engage linguistic reasoning,
but that

doesn't quite feel right. Both of these techniques
force

us to put our questions into words, but words

themselves are tools. We use words to communicate
our

ideas to other people.

As primates, we've evolved a set of social
skills

and behaviors for getting our needs met as
part

of a community. So, while these techniques
do involve

using language centers of your brain, I think
they

reach beyond those centers to tap into our
social

reasoning.

The rubber duck technique works because, putting
your problem

into words forces you to organize your understanding
of

a problem in such a way that you can

verbally lead another mind through it. And
Please, Mr.

Gear? let's us anthropomorphize an object
and talk to

it to discover whether it conforms to the
single

responsibility principle.

To me, the tell-tale phrase in Sandi's description
of

this technique is, asking the question ought
to make

sense. Most of us have an intuitive understanding
that

it might not be appropriate to ask Alice about

something that is Bob's responsibility. Interrogating
an object as

though it were a person helps us use that

social knowledge, and it gives us an opportunity
to

notice that a particular question doesn't
make sense to

ask any of our existing objects, which might
prompt

us to ask if we should create a new

object to fill that role instead.

Now, personally, I would have considered PODR
to have

been a worthwhile purchase if Please, Mr.
Gear was

the only thing I got from it. But, in

this book, Sandi also made what I thought
was

a very compelling case for UML Sequence Diagrams.

Where Please, Mr. Gear is a good tool for

discovering which objects should be responsible
for a particular

method, a Sequence Diagram can help you analyze
the

runtime interaction between several different
objects. At first glance,

this looks kind of like something in the boxes

and arrows category of visual and spatial
tools, but

again, this feels more like it's tapping into
that

social understanding that we have. This can
be a

good way to get a sense for when an

object is bossy or when performing a task
involves

a complex sequence of several, several interactions.
Or if

there are just plain too many different things
to

keep track of.

Rather than turn this into a lecture on UML,

I'm just gonna tell you to go buy Sandi's

book, and if for whatever reason, you cannot
afford

it, come talk to me later and we'll work

something out.

Now for the really hand-wavy stuff. Metaphors
can be

a really useful tool in software. The turtle
graphic

system in Logo is a great metaphor. Has anybody

used Logo at any point in their life? About

half the people. That's really cool.

We've probably all played with drawing something
on the

screen at some point, but most of the rendering

systems that I've used are based on a Cartesian

coordinate system, a grid. And this metaphor
encourages the

programmer to imagine themselves as the turtle,
and to

use that understanding to figure out, when
they get

stuck, what they should be doing next.

One of the original creators of Logo called
this

Body Syntonic Reasoning, and specifically
developed it to help

children solve problems. But the turtle metaphor,
the turtle

metaphor works for everybody, not just for
kids.

Cartesian grids are great for drawing boxes.
Mostly great.

But it can take some very careful thinking
to

figure out how to, how to use x, y

coordinate pairs to draw a spiral or a star

or a snowflake or a tree. Choosing a different

metaphor can make different kinds of solutions
easy, where

before they seemed like too much trouble to
be

worth bothering with.

James Ladd, in 2008, wrote a couple of interesting

blog posts about what he called East-oriented
code. Imagine

a compass overlaid on top of your screen.
In

this, in this model, messages that an object
sends

to itself go South, and any data returned
from

those calls goes North. Communications between
objects is the

same thing, rotated ninety degrees. Messages
sent to other

objects go East, and the return values from
those

messages flow West.

What James Ladd suggests is that, in general,
code

that sends messages to other objects, code
where information

mostly flows East, is easier to extend and
maintain

than code that looks at data and then decides

what to do with it, which is code where

information flows West.

Really, this is just the design principle,
tell, don't

ask. But, the metaphor of the compass, compass
recasts

this in a way that helps us use our

background spatial awareness to keep this
principle in mind

at all times. In fact, there are plenty of

ways we can use our background level awareness
to

analyze our code.

Isn't this adorable? I love this picture.

Code smells are an entire category of metaphors
that

we use to talk about our work. In fact,

the name code smell itself is a metaphor for

anything about your code that hints at a design

problem, which I suppose makes it a meta-metaphor.

Some code smells have names are extremely
literal. Duplicated

code, long method and so on. But some of

these are delightfully suggestive. Feature
envy. Refused bequest. Primitive

obsession. To me, the names on the right have

a lot in common with Please, Mr. Gear. They're

chosen to hook into something in our social
awareness

to give a name to a pattern of dysfunction,

and by naming the problems it suggests a possible

solution.

So, these are most of the shortcuts that I've

accumulated over the years, and I hope that
this

can be the start of a similar collection for

some of you.

Now the part where I try to put the

fear into you. Evolution has designed our
brains to

lie to us. Brains are expensive. The human
brain

accounts for just two percent of body mass,
but

twenty percent of our caloric intake. That's
a huge

energy requirement that has to be justified.

Evolution, as a designer, does one thing and
one

thing only. It selects for traits that allow
an

organism to stay alive long enough to reproduce.
It

doesn't care about getting the best solution.
Only one

that's good enough to compete in the current
landscape.

Evolution will tolerate any hack as long as
it

meets that one goal.

As an example, I want to take a minute

to talk about how we see the world around

us. The human eye has two different kinds
of

photo receptors. There are about a hundred
and twenty

million rod cells in each eye. These play
little

or no role in color vision, and they're mostly

used for night time and peripheral vision.

There are also about six or seven million
cone

cells in each eye, and these give us color

vision, but they require a lot more light
to

work. And the vast majority of cone cells
are

packed together in a tight little cluster
near the

center of the retina. This area is what we

use to focus on individual details, and it's
smaller

than you might think. It's only fifteen degrees
wide.

As a result, our vision is extremely directional.
We

have a very small area of high detail and

high color, and the rest of our field of

vision is more or less monochrome. So when
we

look at this, our eyes see something like
this.

In order to turn the image on the left

into the image on the right, our brains are

doing a lot of work that we're mostly unaware

of.

We compensate for having such highly directional
vision by

moving our eyes around a lot. Our brains combine

the details from these individual points of
interest to

construct a persistent mental model of whatever
we're looking

at. These fast point to point movements are
called

saccades. And they're actually the fastest
movements that the

human body can make. The shorter saccades
that you

make, might make when you're reading, last
for twenty

to forty milliseconds. Longer ones that travel
through a

wider arc might take two hundred milliseconds,
or about

a fifth of a second.

What I find so fascinating about this is that

we don't perceive saccades. During a saccade,
the eye

is still sending data to the brain, but what

it's sending is a smeary blur. So the brain

just edits that part out. This process is
called

saccadic masking. You can see this effect
for yourself.

Next time you're in front of a mirror, lean

in close and look back and forth from the

reflection of one eye to the other. You won't

see your eyes move. As far as we can

tell, our gaze just jumps instantaneously
from one reference

point to the next. And here's where I have

to wait for a moment while everybody stops
doing

this.

When I was preparing for this talk, I found

an absolutely wonderful sentence in the Wikipedia
entry on

saccades. It said, Due to saccadic masking,
the eye/brain

system not only hides the eye movements from
the

individual, but also hides the evidence that
anything has

been hidden.

Hides. The evidence. That anything has been
hidden. Our

brains lie to us. And they lie to us

about having lied to us. And this happens
to

you multiple times a second, every waking
hour, every

day of your life. Of course, there's a reason

for this.

Imagine if, every time you shifted your gaze
around,

you got distracted by all the pretty colors.
You

would be eaten by lions.

But, in selecting for this design, evolution
made a

trade off. The trade off is that we are

effectively blind every time we move our eyes
around.

Sometimes for up to a fifth of a second.

And I wanted to talk about this, partly because

it's a really fun subject, but also to show

that just one of the ways that our brains

are doing a massive amount of work to process

information from our environment and present
us with an

abstraction.

And as programmers, if we know anything about
abstractions,

it's that they're hard to get right. Which
leads

me to an interesting question. Does it make
sense

to use any of the techniques that I talked

about in part one, to try to coral different

parts of our brains into doing our work for

us, if we don't know what kinds of shortcuts

they're gonna take?

According to the Oxford English Dictionary,
the word bias

seems to have entered the English language
around the

1520s. It was used as a, a technical term

in the game of lawn bowling, and it referred

to a ball that was constructed in such a

way that it would curve, it would roll in

a curved path instead of in a straight line.

And since then, it's picked up a few additional

meanings, but they all have that same different
connotation

of something that's skewed or off a little
bit.

Cognitive bias is a term for systematic errors
in

thinking. These are patterns of thought that
diverge in

measurable and predictable ways from what
the answers that

pure rationality might give are. We have some
free

time. I suggest that you go have a look

at the Wikipedia page called List of cognitive
biases.

There are over a hundred and fifty of them

and they are fascinating reading.

And this list of cognitive biases has a lot

in common with the list of code smells that

I showed earlier. A lot of these names are

very literal. But there are a few that stand

out, like cursive knowledge, or the Google
effect or,

and I kid you not, the Ikea effect. But

the parallel goes deeper than that.

This lif - excuse me - this list gives

names to patterns of dysfunction, and once
you have

a name for a thing, it's a lot easier

to recognize it and figure out what to do

about it. I do want to call your attention

to one particular item on this list. It's
called

the bias blind spot. This is the tendency
to

see oneself as less biased than other people,
or

to be able to identify more cognitive biases
in

others than in oneself. Sound like anybody
you know?

Just let that sink in for a minute. Seriously,

though.

In our field, we like to think of ourselves

as more rational than the average person,
and it

just isn't true. Yes, as programmers, we have
a

valuable, marketable skill that depends on
our ability to

reason mathematically. But we do ourselves
and others a

disservice if we allow ourselves to believe
that being

good at programming means anything other than,
we're good

at programming. Because as humans we are all
biased.

It's built into us, in our DNA. And pretending

that we aren't biased only allows our biases
to

run free.

I don't have a lot of general advice for

how to look for bias, but I think an

obvious and necessary first step is just to
ask

the question, how is this biased? Beyond that,
I

suggest that you learn about as many specific
cognitive

biases as you can so that your brain can

do what it does, which is to look for

patterns and make associations and classify
things.

I think everybody should understand their
own biases, because

only by knowing how you're biased can you
then

decide how to con- how to correct for that

bias in the decisions that you make. If you're

not checking your work for bias, you can look

right past a great solution and you'll never
know

it was there.

So for part three of my talk, I have

an example of a solution that is simple, elegant,

just about the last thing I ever would have

thought of.

For the benefit of those of you who have

yet to find your first gray hair, Pac-Man
was

a video game released in 1980 that let people

maneuver around a maze eating dots while trying
to

avoid four ghosts. Now, playing games in fun,
but

we're programmers. We want to know how things
work.

So let's talk about programming Pac-Man.

For the purposes of this discussion, we'll
focus on

just three things. The Pac-Man, the ghosts,
and the

maze. The Pac-Man is controlled by the player.
So

that code is basically just responding to
hardware events.

Boring. The maze is there so that the player

has some chance at avoiding the ghosts. But
the

ghost AI, that's what's gonna make the game
interesting

enough that people keep dropping quarters
into a slot,

and by the way, video games used to cost

a quarter.

When I was your age.

So to keep things simple, we'll start with
one

ghost. How do we program its movement? We
could

choose a random direction and move that way
until

we hit a wall and then choose another random

direction. This is very easy to implement,
but not

much of a challenge for the player.

OK, so, we could compute the distance to the

Pac-Man in x and y and pick a direction

that makes one of those smaller. But then
the

ghost is gonna get stuck in corners or behind

walls cause it won't go around to catch the

Pac-Man. And, again, it's gonna be too easy
for

the player.

So how about instead of minimizing linear
distance, we

focus on topological distance? We can compute
all possible

paths through the maze, pick the shortest
one that

gets us to the Pac-Man and then step down

it. And when we get to the next place,

we'll do it all again.

This works find for one ghost. But if all

four ghosts use this algorithm, then they're
gonna wind

up chasing after the player in a tight little

bunch instead of fanning out. OK. So each
ghost

computes all possible paths to the Pac-Man
and rejects

any path that goes through another ghost.
That shouldn't

be too hard, right?

I don't have a statistically valid sample,
but my

guess is that when asked to design an AI

for the ghosts, most programmers would go
through a

thought process more or less like what I just

walked through. So, how is this solution biased?

I don't have a name, a good name for

how this is biased, so the best way I

have to communicate this idea is to walk you

through a very different solution.

In 2006, I attended Oopsla, this is a conference

put on by the ACM, as a student volunteer,

and I happened to sit in on a presentation

by Alexander Repenning from the University
of Colorado. And

in his presentation, he walked through the
Pac-Man problem,

more or less the way I just did, and

then he presented this idea.

What you do is you give the Pac-Man a

smell, and then you model the diffusion of
that

smell throughout the environment. In the real
world, smells

travel through the air. We certainly don't
need to

model each individual air molecule. What we
can do,

instead, is just divide the environment up
into reasonably

sized logical chunks, and we model those.

Coincidentally, we already do have an object
that does

exactly that for us. It's the tiles of the

maze itself. They're not really doing anything
else, so

we can borrow those as a convenient container
for

this computation. We program the game as follows.

We say that the Pac-Man gives whatever floor
tile

it's standing on a Pac-Man smell value, say
a

thousand. The number doesn't really matter.
And that, that

tile then passes a smaller value off to each

of its neighbors, and they pass a smaller
value

off to each of their neighbors and so on.

Iterate this a few times and you get a

diffusion contour that we can visualize as
a hill

with its peak centered on the Pac-Man.

It's a little hard to see here. The Pac-Man

is at the bottom of that big yellow bar

on the left. So we've got the Pac-Man. We've

got the floor tiles. But in order to make

it a maze, we also have to have some

walls. What we do is we give the walls

a Pac-Man smell value of zero. That chops
the

hill up a bit.

And now all our ghost has to do is

climb the hill. We program the first ghost
to

sample each of the floor tiles next to it,

pick the one with the biggest number, go that

way. It barely seems worthy of being called
an

AI, does it? But check this out. When we

add more ghosts to the maze, we only have

to make one change to get them to cooperate.

And interestingly, we don't change the ghosts'
movement behaviors

at all. Instead, we have the ghosts tell the

floor tile that they're, I guess, floating
above, that

its Pac-Men smell value is zero. This changes
the

shape of that diffusion contour. Instead of
a smooth

hill that always slopes down away from the
Pac-Man,

there are now cliffs where the hill drops
immediately

to zero.

In effect, we turn the ghosts into movable
walls,

so that when one ghost cuts off another one,

the second one will automatically choose a
different route.

This lets the ghosts cooperate without needing
to be

aware of each other. And halfway through this
conference

session that I was sitting in where I saw

this, I was like.

What just happened?

At first, like, my first level of surprise
was

just, what an interesting approach. But then
I got

really, completely stunned when I thought
about how surprising

that solution was. And I hope that looking
at

the second solution helps you understand the
bias in

the first solution.

In his paper, Professor Repenning wrote, The
challenge to

find this solution is a psychological, not
a technical

one. Our first instinct, when we're presented
with this

problem, is to imagine ourselves as the ghost.
This

is the body syntonic reasoning that's built
into Logo,

and in this case it's a trap.

Because it leads us to solve the pursuit problem

by making the pursuer smarter. Once we started
down

that road, it's very unlikely that we're going
to

consider a radically different approach, even,
or, perhaps, especially

if it's a very much simpler one. In other

words, body syntonicity biases us towards
modeling objects in

the foreground, rather than objects in the
background.

Oops, sorry.

OK. Does this mean that you shouldn't use
body

syntonic reasoning? Of course not. It's a
tool. It's

right for some jobs. It's not right for others.

I want to take a look at one more

technique from part one. What's the bias in
Please

Mr. Gear, what is your ratio? Aside from the

gendered language, which is trivially easy
to address. This

technique is explicitly designed to give you
an opportunity

to discover new objects in your model. But
it

only works after you've given at least one
of

those objects a name.

Names have gravity. Metaphors can be tar pits.
It's

very likely that the new objects that you
discover

are going to be fairly closely related to
the

ones that you already have. Another way to
help

see this is to think about how many steps

it takes to get from Please, Ms. Pac-Man,
what

is your current position in the maze? To,
please

Ms. Floor Tile, how much do you smell like

Pac-Man?

For a lot of people, the answer to that

question is probably infinity. It certainly
was for me.

My guess is that you don't come up with

this technique unless you've already done
some work modeling

diffusion in another context. Which, incidentally,
is why I

like to work on diverse teams. The more different

backgrounds and perspectives we have access
to, the more

chances we have to find a novel application
of

some seemingly unrelated technique, because
somebody's worked with it

before.

It can be exhilarating and very empowering
to find

these techniques that let us take shortcuts
in our

work by leveraging these specialized structures
in our brains.

But those structures themselves take shortcuts,
and if you're

not careful, they can lead you down a primrose

path.

I want to go back to that quote that

got me thinking about all this in the first

place. About how we don't ever teach anybody
how

to do that or even that they should.

Ultimately, I think we should use techniques
like this,

despite the, the biases in them. I think we

should share them. And I think, to paraphrase
Glenn,

we should teach people that this is a thing

that you can and should do. And, I think

that we should teach people that looking critically
at

the answers that these techniques give you
is also

a thing that you can and should do.

We might not always be able to come up

with a radically simpler or different approach,
but the

least we can do is give ourselves the opportunity

to do so, by asking how is this biased?

I want to say thank you, real quickly, to

everybody who helped me with this talk, or
the

ideas in it. And also thank you to LivingSocial

for paying for my trip. And also for bringing

these wonderful brains. So, they're gonna
start tearing this

stage down in a few minutes. Rather than take

Q and A up here, I'm gonna pack up

all my stuff and then I'm gonna migrate over

there, and you can come and bug me. pick

up a brain. Whatever.

Thank you.