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Hi! I'm Nina Strohminger.

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I work at Yale University in the[br]School of Management and

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the department a cognitive science.

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And I'm Shaun Nichols

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

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Imagine it's the not-distant future

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and you're in a car crash.

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Part of your brain is[br]damaged in the crash,

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and the doctors have to[br]replace it with a microchip.

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But the microchip is faulty, and it doesn't

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completely restore every[br]part of your mind.

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One way it could malfunction[br]is it could lead you to

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no longer be able to identify objects.

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This is called "visual object agnosia."

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Another malfunction the microchip[br]is capable of producing

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is it removes all of your[br]desires and interests:

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music you like, your hobbies,[br]your goals for the future.

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The microchip can also lead to amnesia

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for all your experiences[br]prior to the crash.

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

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your ability to know the difference[br]between right and wrong.

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For which of these injuries to your mind

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would your identity be the most altered?

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Philosophy has provided[br]multiple conjectures

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about the answer to[br]this kind of question.

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Some philosophers, like Bernard Williams,[br]have suggested that biological continuity,

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

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

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is the addition of the[br]microchip to your brain,

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because that's changing[br]the organismic properties.

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So it's not the changes to the[br]psychological function that

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matter primarily in this case.

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It's the changes to the[br]biology that matter.

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An alternative account is the collection[br]of psychological traits,

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

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

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person from another seem that they'd be

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likely candidates for being a critical[br]part of personal identity.

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

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cause the greatest change to identity.

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Memory has traditionally been seen as

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playing an especially crucial[br]role in personal identity.

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John Locke illustrates this idea with a

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thought experiment about[br]a prince and a cobbler.

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

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

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This new individual, is he[br]the prince or the cobbler?

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

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

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More recently, it's been suggested that

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morality is the most important[br]part of identity.

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Cultural folklore provides indirect[br]evidence in favor of this idea.

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For instance, in Western[br]religious traditions,

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

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but as the source of our[br]conscience and moral action.

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

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given much attention in[br]philosophical circles.

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Despite the central position[br]this question has

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occupied in philosophical debates,

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it's only been recently that[br]philosophers began collecting data

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to show how people actually[br]conceive of personal identity.

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

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

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To find out, Shaun and I ran a study where

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we presented subjects with the[br]microchip thought experiment.

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

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leads to the greatest change[br]in someone's identity.

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The elimination of memories and desires

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also leads to a substantial change[br]in identity, subjects report,

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

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Basic psychological processes,

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like object recognition, are not

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particularly important to[br]identity permanence.

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And mere physical changes, such as

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installing the microchip[br]that perfectly preserves

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

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When people consider what[br]makes someone who they are,

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they place central importance[br]on moral capacity.

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

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

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

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

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identity isn't really distinctiveness.

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It's the moral traits.

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

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identity than traits that[br]are more distinctive.

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

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a much more dramatic[br]insult to one's identity

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than losing some highly unusual[br]preference, like a penchant for,

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

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

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age-old philosophical problems.

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While data can't provide[br]a definitive answer[br]

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to the metaphysical question[br]of what ought identity to be,

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