Philosophy (Psychology): Personal Identity

Using the method of experimental philosophy, Nina Strohminger (Yale University) and Shaun Nichols (University of Arizona) compare philosophical and everyday answers to the question "Which aspect of the self is most essential for personal identity?"

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(intro music)

Hi! I'm Nina Strohminger.

I work at Yale University in the
School of Management and

the department a cognitive science.

And I'm Shaun Nichols

I'm a professor of philosophy
at the University of Arizona.

Imagine it's the not-distant future

and you're in a car crash.

Part of your brain is
damaged in the crash,

and the doctors have to
replace it with a microchip.

But the microchip is faulty, and it doesn't

completely restore every
part of your mind.

One way it could malfunction
is it could lead you to

no longer be able to identify objects.

This is called "visual object agnosia."

Another malfunction the microchip
is capable of producing

is it removes all of your
desires and interests:

music you like, your hobbies,
your goals for the future.

The microchip can also lead to amnesia

for all your experiences
prior to the crash.

Finally, the microchip could lead
you to lose your moral compass,

your ability to know the difference
between right and wrong.

For which of these injuries to your mind

would your identity be the most altered?

Philosophy has provided
multiple conjectures

about the answer to
this kind of question.

Some philosophers, like Bernard Williams,
have suggested that biological continuity,

having the same organism, is the
most important part of identity.

On this view, the aspect of the scenario
that would alter your identity the most

is the addition of the
microchip to your brain,

because that's changing
the organismic properties.

So it's not the changes to the
psychological function that

matter primarily in this case.

It's the changes to the
biology that matter.

An alternative account is the collection
of psychological traits,

like personality traits and preferences,
that that's the basis for identity.

In particular, the mental features that
most allow us to differentiate one

person from another seem that they'd be

likely candidates for being a critical
part of personal identity.

If that view is correct, then losing one's
distinctive desires in memory should

cause the greatest change to identity.

Memory has traditionally been seen as

playing an especially crucial
role in personal identity.

John Locke illustrates this idea with a

thought experiment about
a prince and a cobbler.

Imagine the mind of a prince, containing
all the prince's past experiences

were to enter into, and replace, the
Cobbler's memories and experiences.

This new individual, is he
the prince or the cobbler?

Locke think the answer is really
obvious: of course this is the prince!

It's just that, now, the prince is
inhabiting the body the cobbler.

More recently, it's been suggested that

morality is the most important
part of identity.

Cultural folklore provides indirect
evidence in favor of this idea.

For instance, in Western
religious traditions,

souls are seen not only as an entity
that lends us our unique identity,

but as the source of our
conscience and moral action.

However, the view that morality is key
to identity has not traditionally been

given much attention in
philosophical circles.

Despite the central position
this question has

occupied in philosophical debates,

it's only been recently that
philosophers began collecting data

to show how people actually
conceive of personal identity.

Locke believed that memories were
the most important part of identity,

but does this map onto the way people
actually think about identity?

To find out, Shaun and I ran a study where

we presented subjects with the
microchip thought experiment.

People in this study overwhelmingly
report that loss of the moral faculty

leads to the greatest change
in someone's identity.

The elimination of memories and desires

also leads to a substantial change
in identity, subjects report,

just not as dramatic as one produced
by a loss of moral capacities.

Basic psychological processes,

like object recognition, are not

particularly important to
identity permanence.

And mere physical changes, such as

installing the microchip
that perfectly preserves

mental function leads to the lowest
degree of perceived identity change.

When people consider what
makes someone who they are,

they place central importance
on moral capacity.

and this runs counter to perhaps the
best-known theory of personal identity,

Locke's memory criterion, according
to which you're the same person

just in case you remember having the
experience of some past person.

In other studies, we've found what people
regard as most important about

identity isn't really distinctiveness.

It's the moral traits.

And the moral traits that people have can
be commonplace, and yet more critical to

identity than traits that
are more distinctive.

So for instance, many people are nice, but
losing that common trait is regarded as

a much more dramatic
insult to one's identity

than losing some highly unusual
preference, like a penchant for,

I don't know, watermelon
infused with beef juice.

This study also illustrates the power
of empirical data to shed light on

age-old philosophical problems.

While data can't provide
a definitive answer

to the metaphysical question
of what ought identity to be,

it can tell us how we think about
our identities in everyday life.