Would you sacrifice one person to save five? - Eleanor Nelsen

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Imagine you’re watching a runaway trolley barreling down the tracks, straight towards five workers. You happen to be standing next to a switch that will divert the trolley onto a second track. Here’s the problem: that track has a worker on it, too — but just one. What do you do? Do you sacrifice one person to save five? Eleanor Nelsen details the ethical dilemma that is the trolley problem.

Lesson by Eleanor Nelsen, animation by Eoin Duffy.

Imagine you're watching a runaway trolley
barreling down the tracks

straight towards five workers
who can't escape.

You happen to be standing next to a switch

that will divert the trolley
onto a second track.

Here's the problem.

That track has a worker on it, too,
but just one.

What do you do?

Do you sacrifice one person to save five?

This is the trolley problem,

a version of an ethical dilemma that
philosopher Philippa Foot devised in 1967.

It's popular because it forces us
to think about how to choose

when there are no good choices.

Do we pick the action
with the best outcome

or stick to a moral code that prohibits
causing someone's death?

In one survey, about 90% of respondents
said that it's okay to flip the switch,

letting one worker die to save five,

and other studies, including a virtual
reality simulation of the dilemma,

have found similar results.

These judgments are consistent with the
philosophical principle of utilitarianism

which argues that
the morally correct decision

is the one that maximizes well-being
for the greatest number of people.

The five lives outweigh one,

even if achieving that outcome requires
condemning someone to death.

But people don't always take
the utilitarian view,

which we can see by changing
the trolley problem a bit.

This time, you're standing on a bridge
over the track

as the runaway trolley approaches.

Now there's no second track,

but there is a very large man
on the bridge next to you.

If you push him over,
his body will stop the trolley,

saving the five workers,

but he'll die.

To utilitarians,
the decision is exactly the same,

lose one life to save five.

But in this case, only about 10% of people

say that it's OK to throw the man
onto the tracks.

Our instincts tell us that deliberately
causing someone's death

is different than allowing them to die
as collateral damage.

It just feels wrong for reasons
that are hard to explain.

This intersection between ethics
and psychology

is what's so interesting
about the trolley problem.

The dilemma in its many variations reveal
that what we think is right or wrong

depends on factors other than
a logical weighing of the pros and cons.

For example, men are more likely
than women

to say it's okay to push the man
over the bridge.

So are people who watch a comedy clip
before doing the thought experiment.

And in one virtual reality study,

people were more willing
to sacrifice men than women.

Researchers have studied
the brain activity

of people thinking through the classic
and bridge versions.

Both scenarios activate areas of the brain
involved in conscious decision-making

and emotional responses.

But in the bridge version,
the emotional response is much stronger.

So is activity in an area of the brain

associated with processing
internal conflict.

Why the difference?

One explanation is that pushing someone
to their death feels more personal,

activating an emotional aversion
to killing another person,

but we feel conflicted because we know
it's still the logical choice.

"Trolleyology" has been criticized by some
philosophers and psychologists.

They argue that it doesn't reveal anything
because its premise is so unrealistic

that study participants
don't take it seriously.

But new technology is making this kind
of ethical analysis

more important than ever.

For example, driver-less cars
may have to handle choices

like causing a small accident
to prevent a larger one.

Meanwhile, governments are researching
autonomous military drones

that could wind up making decisions of
whether they'll risk civilian casualties

to attack a high-value target.

If we want these actions to be ethical,

we have to decide in advance
how to value human life

and judge the greater good.

So researchers who study
autonomous systems

are collaborating with philosophers

to address the complex problem
of programming ethics into machines,

which goes to show that
even hypothetical dilemmas

can wind up on a collision course
with the real world.