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  • Professor Paul Bloom: What we've been talking about

  • so far in the course are human universals, what everybody

  • shares. So, we've been talking about

  • language, about rationality, about perception,

  • about the emotions, about universals of

  • development, and we've been talking about what people share.

  • But honestly, what a lot of us are very

  • interested in is why we're different and the nature of

  • these differences and the explanation for them.

  • And that's what we'll turn to today.

  • So first, we'll discuss how are people different,

  • different theories about what makes you different in a

  • psychological way from the person sitting next to you,

  • and then we'll review different theories about why people are

  • different. And this is the class which is

  • going to bother the most people. It's not dualism.

  • It's not evolution. It's this because the

  • scientific findings on human psychological differences are,

  • to many of us, shocking and unbelievable.

  • And I will just try to persuade you to take them seriously.

  • Okay. So, how are people different?

  • Well, there's all sorts of ways. Your sexual identity--It is at

  • the core of your being for almost all of us whether you're

  • male or female. How we refer to you in

  • language, what pronoun we use, is indexed on how we--on

  • your--on how--whether you're male or female and related to

  • that though imperfectly is your sexual orientation,

  • who you're attracted to. The question of why some of us

  • think of ourselves as males and others as females,

  • and the question of why some of us would ideally want to have

  • sex with males, others with females,

  • others with both, and then a few others who have

  • harder to define desires, is such a good question that

  • we're going to talk about it after spring break while all the

  • sexual desire has been spent and you could focus on [laughter]

  • on a scientific discussion of this--not that I recommend you

  • do that on spring break. How happy are you?

  • This is also such a good topic it's going to get its own class.

  • The very last class of the semester is devoted to happiness

  • and the question of what makes people happy,

  • what makes people unhappy, and what makes people differ in

  • their happiness. If I asked you to rank how

  • happy you are from a scale of 1 to 10, the numbers would differ

  • across this room. And there's different theories

  • as to why. Your success and failure in

  • life--This is somewhat interesting because you could

  • study this in more or less objective ways.

  • We don't have to ask people. We could look at your

  • relationships, how they begin,

  • how they end, your job satisfaction.

  • We could look at your criminal records.

  • Some of you are going to see time.

  • Most will not. Some of you will get into

  • little troubles all through your life.

  • Some of you already have seen the inside of a police station,

  • possibly a lineup. Others couldn't go near such a

  • thing. What determines that?

  • And at the root of all human differences are two main

  • factors. And so, I want to talk about

  • the two main interesting factors.

  • One is personality. The other is intelligence.

  • And this is what--These are the differences I'll talk about

  • today first from the standpoint of how do we characterize them,

  • how do we explain them, and then from the standpoint of

  • why these differences exist in the first place.

  • One way to characterize personality is in terms of

  • people's style with dealing with--in dealing with the world

  • and particularly their style with dealing--in dealing with

  • other people. So, you take a simple character

  • you know of and you could talk about that person's personality.

  • You could talk about it in terms of being impulsive,

  • irresponsible, sometimes lazy,

  • good-hearted. You could compare that person's

  • personality with other people's personalities such as my

  • colleague who gave a talk last class.

  • He's wonderful. He's responsible and reliable

  • and very kind [laughter] and different from Homer.

  • And so, this difference is a difference in personality.

  • Now, when we talk about personality we're talking about

  • something else as well. We're talking about a stable

  • trait across situations and time.

  • So, if all of a sudden the person next to you kind of

  • smacks you in the head, you might be angry but we

  • wouldn't call that "personality" because that's something that's

  • a result of a situation. We'd all feel that way in that

  • situation. It's "personality" if you walk

  • around all the time angry. That'd be a stable trait.

  • That'd be something you carry around with you and that's what

  • we mean by personality. Now, how do we scientifically

  • characterize differences in personality?

  • And it's a deep question. There's been a lot of attempts

  • to do so. Any assessment has--Any good

  • assessment has to satisfy two conditions.

  • And these are terms which are going to show up all over

  • psychological research but it's particularly relevant for this

  • sort of measure. One is "reliability."

  • Reliability means there is not measurement error.

  • And one crude way to think about reliability is,

  • a test is reliable if you test the same person at different

  • times and you get the same result.

  • My bathroom scale is reliable if whenever I stand on it,

  • it gives me more or less the same number.

  • It's not reliable if it's off by ten pounds in the course of a

  • day. Similarly, if I give you a

  • personality test now and it says that you're anxious and

  • defensive, well--and then give it to you

  • tomorrow and it says you're calm and open minded,

  • it's not a reliable test. So, reliable is something you

  • could trust over time. "Validity" is something

  • different. Validity is that your test

  • measures what it's supposed to measure.

  • So, validity means it's sort of a good test.

  • Forget about how reliable it is. Does it tap what you're

  • interested in? So, for example,

  • suppose I determine your intelligence by the date of your

  • birth. I figure out what day you were

  • born and I have a theory that, from that, predicts how smart

  • you are. That's my intelligence test,

  • the date of your birth. Maybe people born in January

  • are the dumbest, people born in December are the

  • smartest. Is that--I was born on

  • Christmas Eve. [laughter]

  • Is that a reliable test? Yes, it's a wonderfully

  • reliable test. I'll test you today;

  • I'll test you tomorrow; I'll test you next year;

  • I'll test you the day you die; I'll get the same IQ score.

  • Is it a valid test? It's a joke.

  • It's absolutely not a valid test.

  • It has nothing to do with intelligence.

  • But you noticed these are two different things.

  • Something can be reliable but not valid and something can be

  • valid and not reliable. Now, there are no shortage of

  • personality tests. You could get them all over the

  • place including on the web. So, I took one recently.

  • I took "which super hero are you?"

  • [laughter] And it's a series of questions

  • determining what super hero you are.

  • You could take this yourself if you want to.

  • The same web page, by the way, offers you a test

  • in whether you're "hot" or not. We'll discuss that later.

  • And when I did this [laughter] it told me I was Batman

  • [laughter] and "you are dark,

  • love gadgets, and have vowed to help the

  • innocent not suffer the pain you have endured."

  • Now, the honest-- [laughter] Now, to be honest though,

  • it's neither reliable nor valid.

  • When I first did the test I came up as "The Incredible

  • Hulk." I then changed my answers a bit

  • and was "Wonder Woman." [laughter]

  • And finally, out of frustration,

  • I carefully tailored my answers so I would be Batman.

  • But the fact that I can do that, well, raises questions

  • about both the reliability of this measure and its validity.

  • Here is an example – a real world example.

  • This is, in black and white form, a version of the Rorschach

  • test, the Rorschach inkblot test.

  • How many people have heard of the Rorschach test?

  • Okay. Is there anybody here who has

  • actually, in any sort of situation, taken a Rorschach

  • test? Some people scattered in the

  • room have taken them. It was originally used only for

  • psychiatric cases but then became extremely common.

  • About eighty percent of clinical psychologists claim to

  • use it and most graduate programs in the American

  • Psychological Association who are accredited teach it.

  • Catholic seminaries use it for people who want to join the

  • seminary. It was invented by a guy named

  • Herman Rorschach. He devoted his entire life to

  • the inkblot test. His nickname when he was a

  • teenager – I am not kidding youwas "Inkblot."

  • [laughter] And the idea is by looking at

  • these inkblots and then seeing what somebody says you get great

  • insights into the nature of their personality,

  • into what they are. Anybody want to try it?

  • Come on. Yes.

  • What do you see? Student:

  • I see two people holding hands pressed together.

  • Professor Paul Bloom: Two people holding hands pressed

  • together. Very good.

  • Anybody have a different reading?

  • Yes, in back. Yes.

  • Yes. Student: Dancing bears.

  • Professor Paul Bloom: Dancing bears.

  • Okay. Good.[laughter] Good.

  • Okay. I got to write your name down--

  • [laughs][laughter] report you to health-- No.

  • Dancing bears, very good. Anybody else?

  • One other. Yes.

  • Student: A man in a ski mask.

  • Professor Paul Bloom: A man in a ski mask.

  • Well, it turns out that there are right answers and wrong

  • answers to the Rorschach test. According to the test,

  • and this is from a real Rorschach test,

  • "it is important to see the blot as two human figures,

  • usually females or clowns." Good work over there.

  • "If you don't, it's seen as a sign you have

  • problems relating to people." [laughter]

  • If you want to go for "a cave entrance" or "butterfly" or

  • "vagina," that's also okay. [laughter]

  • Now, the Rorschach test is transcendently useless.

  • It has been studied and explored and it is as useless as

  • throwing dice. It is as useless as tea leaves.

  • Nonetheless, people love it and it's used

  • all over the place. It is used for example in child

  • custody cases. If you have broken up with your

  • partner and you guys are quarreling over who gets to keep

  • the kids, you might find yourself in a

  • shrink's office looking at this. And in fact,

  • this is why they end up on the web.

  • There are services. There are people who have been

  • kind enough to put on the web these inkblots,

  • including the right answers to them.

  • But they are worthless as psychological measures.

  • Can we do better? Well, we probably can.

  • Gordon Allport did a study where he went through the

  • dictionary and took all of the traits that he believed to be

  • related to personality and he got eighteen thousand of them.

  • But what was interesting was they weren't necessarily

  • independent traits. So, the traits like "friendly,

  • sociable, welcoming, warm-hearted" seemed to all tap

  • the same thing. So, Cattell and many others

  • tried to narrow it down, tried to ask the question,

  • "In how many ways are people's personalities different from one

  • another?" How many parameters of

  • difference do you need? How many numbers can I give you

  • that would narrow you in and say what personality you are?

  • One approach was from Eysenck, who claimed there were just

  • two. You could be somewhere on the

  • scale of introverted-extroverted,

  • and somewhere on the scale of neurotic and stable.

  • And since there's basically two types of traits with two

  • settings for each, there are basically four types

  • of people. Later on he added another trait

  • which he described as "psychoticism versus

  • non-psychoticism" that crudely meant whether you're aggressive

  • or empathetic. And then you have three traits

  • with two settings each giving you eight types of people.

  • Later on Cattell dropped it down into sixteen factors.

  • So, these sixteen personality factors are sixteen ways people

  • would differ. And so, if I asked you to

  • describe your roommate along these sixteen dimensions,

  • you should be able to do so. More recently,

  • people have come to the conclusion that two or three is

  • too few, but sixteen might be too many.

  • And there's a psychological consensus on what's been known

  • as "The Big Five." And "The Big Five" personality

  • factors are these, and what this means is when we

  • talk about each other and use adjectives,

  • the claim is we could do so in thousands of different ways,

  • but deep down we're talking about one of these five