[♪INTRO]
Let’s be honest: No one really enjoys airport
security.
It’s annoying, it can take forever,
and it seems like the rules are always changing.
People tell pollsters that they’d fly more
if security wasn’t such a hassle,
but most people also say they’re fine sacrificing
some privacy for more security.
But those screening areas where no one knows
what to do with their shoes
are only one small part of it all.
Every airport is an onion of security measures
that all work together,
and those layers are constantly shifting and evolving.
Over the last 10 years or so, at least in
the United States,
some of that evolution has been inspired by game theorists.
These researchers have been helping decide where security should be,
how much there should be, and how often it should change.
And one common response to all those questions has been: be random.
Game theory is a broad subject that sits in
between math and economics.
It originally focused on how people play games, like the name suggests.
So a game theorist might work out when to bluff in poker,
or why your friend Camille always hoards sheep
in Catan.
But while some researchers still do study
actual games,
the field has expanded far beyond those early
roots.
Plenty of today’s game theorists are looking
at other situations
where intelligent actors (like groups of people)
interact with each other and make decisions.
So things like soldiers making choices on
the battlefield,
businesses competing against each other, or
even election results.
Or Braess’s Paradox from our video about
reducing traffic.
That’s straight out of game theory.
Adding more roads can make traffic worse,
not better.
Because we all try to make our own trip faster,
which ends up making everyone’s drive slower,
including our own.
Governments and businesses also bring in game
theorists
to help with crucial decisions or to build
new systems.
Like, imagine that you run an international
airport in a large city,
and you’ve stopped a few people
who were planning to attack the airport in
the past.
So you want police watching for anything suspicious,
you want dogs sniffing for anything suspicious,
and you want security checking people’s
belongings…
for anything suspicious.
But you only have a certain amount of money,
a certain number of officers and dogs,
and you don’t want everyone to completely
hate your airport
because security takes five hours.
So what do you do?
You call a game theorist.
At least, that’s what they did in LA back
in 2007.
Now, to be totally clear, whether security
screenings and the TSA
are the most effective way to find or stop
threats
is a completely different question
from the one these researchers are trying
to answer.
So the goal, both for these researchers and
in this video,
isn’t to dig into the science or sociology
of security protocols in general.
We’re just going to explain where game theory
has been implemented
at airports so far, and what the reported
results and criticisms have been.
And this all really started at LAX, the Los
Angeles International Airport.
The Los Angeles World Airport Police
wanted checkpoints along the roads to LAX,
but there weren’t enough police to cover
every entrance every day.
So LAX contacted a professor named Milind
Tambe
and asked what they should do.
Together, they developed a computer program
called ARMOR,
short for Assistant for Randomized Monitoring
Over Routes.
It generates recommended security schedules
for the airport.
ARMOR is based on a kind of game theory called
Stackelberg game theory.
In Stackelberg games, one person makes a move
while the second watches,
and then the second has to respond to their
move.
The model is usually applied
to businesses competing against each other
to sell something.
One business goes first and charges what they
want for, say, a T-shirt.
Then other businesses have to respond and
choose what they want to charge
for their own cool, nerdy T-shirts
so that people still want to buy them,
but they’re not so cheap that the business
loses money.
But since the first business knows
that others are going to respond to their
initial decision,
that changes what the first business does
at the beginning.
So before anyone does anything,
you end up with a sort of
“they know that we know that they know that
we know…” kind of situation.
Tambe and other researchers have realized
that Stackelberg games can also apply to security
situations.
The first player is the airport, setting up
their security in a certain way.
The second player is someone trying to attack
the airport
or even just bring something dangerous through
security.
Each player gets to see what the other does
attackers can go to the airport and look at
the security,
and security can monitor attackers whenever
they catch something.
So based on the optimal strategy in certain
kinds of Stackelberg games,
Tambe and the rest of the researchers who
were asked for input
said that the solution to LAX’s problem
was more randomness.
If they couldn’t cover every entrance with
police every single day,
they also shouldn’t have a regular schedule
for which ones are guarded.
Like, if the airport had 6 entrances,
you shouldn’t have police checkpoints at
entrances 1, 2, and 3 on Day 1,
then 2, 3, and 4 on Day 2, then 3, 4, and
5 on Day 3.
Because it’s not too hard to figure out
that on Day 107, entrances 5, 6, and 1 will
be covered,
and entrances 2, 3, and 4 won’t be.
The same goes for paths taken by police dogs
patrolling the airport.
If they regularly followed the same route,
you could predict where they’d be at a certain
time of day.
In these non-random cases, with the right
information, someone could
sneak through an unguarded door or know they
won’t run into a dog.
Even if the schedules seem complex
to someone who’s not paying close attention,
if they have a structure, they can probably
be exploited.
A key element of ARMOR is also that
humans shouldn’t try to put randomness into
the schedule ourselves.
That’s not enough.
Because no matter how “LOL SO RANDOM”
we think we are,
humans just aren’t good at producing or
identifying random sequences.
Our brains just like patterns too much.
One of the simplest examples is that
if researchers have people imagine a coin
flip,
about 80% will say “heads” came up.
Because when we talk about coin flips, we
usually say “heads” first.
Seriously.
So instead, Tambe and the other researchers
designed ARMOR to produce
a mathematically random schedule, without
a discernible pattern in it.
The program was also flexible enough to adjust
based on new information
or pressing security concerns.
Like, if a certain entrance will be way busier
than usual one day,
you’d probably want more security there
than usual.
After six months of ARMOR,
the airport police were very positive about
the program.
A few potential threats, like cars carrying
weapons,
were arrested by officers scheduled by ARMOR.
The new random schedule also reportedly made
police seem more present
at the airport,
and the program reduced the scheduling work
of the people in charge
letting them do other work, instead.
ARMOR was successful enough at LAX that soon,
Tambe was one of a number of researchers hired
by the TSA
to apply game theory to airports across the
US.
There are hundreds of airports nationwide,
and they’re all different.
Each one has its own baggage area and ticket
counters
and terminals and security desks
so you can’t have the exact same security
strategy at each one.
For one thing, that would be super expensive.
The TSA’s budget might be large, but it’s
not that large.
Plus, it’s just not necessary.
Some airports are more threatened than others.
That doesn’t mean the whole budget should
just be thrown at large airports
like LAX, either, though.
Because leaving the rest without security
is a… bad idea.
The team’s first step was a program called
IRIS,
which stands for Intelligent Randomization
In Scheduling.
It adapted the kinds of Stackelberg games
used for ARMOR to schedule
where Federal Air Marshals,
a kind of in-flight security and police force,
should be flying.
Then, they developed GUARDS:
Game-theoretic Unpredictable and Randomly
Deployed Security.
Clearly, they really like a good acronym.
With GUARDS, they didn’t just look at handling
one thing at a time,
like which roads to secure or which Air Marshals
to put onto which flights.
GUARDS is focused on the upper layer of organization:
Where and how the TSA should monitor each
airport
so that they’re all as safe as possible,
without any predictable patterns.
This means that GUARDS also had to take different
security measures
and types of attackers into account.
Someone aiming for the ticket window likely
has different goals
and strategies than someone targeting the
planes.
Since these game theory-based approaches seem
to have been effective
so far, we’ll probably keep seeing more
of them.
But that doesn’t mean they’re perfect,
either.
GUARDS isn’t designed to handle all the
nuances of the real world,
and it can’t dictate how every nook and
cranny of every airport
in the country should be run.
It’s still just a computer program running
with a set of variables,
and can’t include every possible threat
in its scheduling calculations.
And to schedule well, each threat that it
does handle has to be rated
like, essentially on a scale of 0-10.
Which obviously has its problems and subjectivity.
But in 2011, GUARDS was submitted to the TSA
to be tested
at an undisclosed airport.
And if it was successful,
the TSA planned to incorporate the program
into their scheduling elsewhere.
Although since then, they’ve been pretty
quiet about what happened.
Which is… understandable.
That’s a security measure too.
Game-theoretic approaches to security also
don’t stop at the airport.
Tambe and other researchers have branched
out
and developed a program called PROTECT,
or Port Resilience Operational/Tactical Enforcement
to Combat Terrorism.
And it helps protect the port of Boston.
Ports are huge, open spaces; they’re dealing
with boats
and they’re not contained in the same way
that airports are.
Which means that the techniques that worked
in an airport
might not work in a port, and PROTECT accounts
for that.
According to the researchers, it uses a more
accurate model than ARMOR
or GUARDS for how people make decisions, and
it includes more information
about which points are more important to watch
than others.
After recent incidents, researchers have also
proposed ways
to use game theory to protect public spaces
during events.
But that’s an even harder problem!
You have another big space, but it’s crowded
with people
and there are a near-infinite number of things
that could happen.
They’ve even proposed using game theory
to address something
that might seem completely unrelated: protecting
animals from poaching.
Illegal poaching, fishing, and logging are
huge environmental problems,
but they keep happening because it’s impossible
to watch everything at once.
By treating poachers like opponents in certain
kinds of games,
and looking at where they’ve gone so far,
game theorists can try and predict where they’ll
strike next.
Plus, poaching, fishing, and logging are all
much more common
than any other type of attack we’ve talked
about so far.
That’s not a good thing, but it does mean
that after game theorists
have made predictions, it’s easier to check
what actually happened.
That lets them see whether their models do
a better job of protecting
lives than what we’re doing now, and update
them to do better in the future.
So whether it’s airports or wildlife preserves,
game theorists are out there trying to make
the world better for us
and all of our sheep-hoarding, Catan-playing
friends.
Thanks for watching this episode of SciShow!
If you want to learn more about game theory
and the science of decision making,
we have a whole video explaining some of the
basics.
And if you want to keep up with all sorts
of deep dives into science topics,
you can click subscribe.
[♪OUTRO]
