We received a wonderful example of -- for
the kinds of bargains we studied
in the weeks on inductive reasoning.
We studied generalization, and we studied
applications of those generalizations.
And using that for causal reasoning that
we tested by manipulations
and by the sufficient condition tests,
and all of those are brought together
in a wonderful little video.
So, take a look.
>> Hello.
My name's Catriona, and I live in Sweden.
I've spent many years, eating a little bit
of chocolate everyday.
And I've always strongly believed that
eating chocolate makes you happier.
In other words, most people will be
in a better mood
after they've eaten chocolate
than before.
And I'll give you four pieces of evidence
in support of my conclusion.
Evidence one: I've met a lot of people
over the years
and when I give them some of my chocolate,
they always seem happy about it.
I can't think of a single case
of someone eating chocolate
who hasn't looked satisfied afterwards.
Evidence two: It could be that
eating chocolate isn't really causing
their happiness.
They're just happy people eating
chocolate.
So, I asked unhappy people whether they
ever eat chocolate.
And they confirmed that they do,
precisely because it cheers them up.
Evidence three:
Now, I went to a chocolate factory where
the workers get free chocolate every day.
And these people could theoretically be
unhappy like the rest of us could.
but they all had smiles on their faces,
and some smears of chocolate.
Evidence four: You may ask whether these
people are also in love
and it's love that's causing
the happiness,
not actually the chocolate.
So I had to find people who eat chocolate,
but are not in love.
I did a mini survey at my corner shop.
And 80% of the people who responded that
they were not in love,
reported that they definitely felt
their mood improve
when they ate chocolate.
So, it does seem to be the case that
eating chocolate is probably sufficient
to improve your mood.
Obviously there are people who never eat
chocolate and are very happy.
For example a successful dieter
or your dentist.
You can find happiness by falling in love
or getting promoted
or finally reaching the top of Mt.
Everest, whatever's your biggest dream.
But for an instant helping of happiness,
chocolate will cheer you up, mm.
>> Wasn't that great?
I already knew that I loved chocolate
and that it improved my mood,
so maybe I was convinced
by this argument
because, I already believed
the conclusion.
And that's when you ought to be careful.
When you look at an argument, and it's for
a conclusion you already believed,
then there's going to be a tendency
to think it's a great argument.
so if you really want to know
whether it is or is not a good argument.
You gotta look carefully at the ones that
are trying convince you
of things that already had a tendency to
believe in the first place.
So let's look carefully at her conclusion.
Catriona's conclusion was very carefully
qualified.
On the one hand, she said that chocolate
is one of the things that makes you happy.
She doesn't claim that it's the only thing
that makes you happy: you know,
Love might make you happy, climbing
Mount Everest might make you happy,
all kinds of things can make you happy.
She's only claiming that
chocolate's one of them.
Another qualification, is that she says
chocolate will probably
improve your mood.
She don't say it's definitely,
don't say it works always,
or for all people.
But it'll probably improve your mood:
so it's an inductive argument,
and she doesn't have to prove it
beyond a shadow of a doubt.
That's a good move in an argument,
because it's very hard to prove things
beyond a shadow of a doubt.
But there is one part of her conclusion
that makes the argument difficult.
And that's that she says chocolate
improves your mood.
Now that's a causal claim.
That's not just that you eat chocolate
and you also happen to be happy.
That's that eating chocolate causes you
to be happier than you were before,
that is, to be in a better mood
than you were before.
So let's see if the different bits of
evidence that she presents
really do support that conclusion.
So the first bit of evidence
that Catriona provides is this.
"Now I've met a lot of people, over the
years, and whenever
I give them some of my chocolate they're
clearly happy about it."
What kind of argument is that?
That is a statistical generalization
from a sample,
because she hadn't met
everybody in the world,
she's only met some people.
But the sample that she's been able to
check, they've all liked chocolate.
She adds one more claim:
"I can't think of a single case of
someone eating chocolate
and not looking satisfied afterwards."
You know, this is kind of repetitious,
because she says
she can't think of a case.
She just told you that whenever she gives
them chocolate, then they're happy
and if they're happy they're satisfied,
and so maybe that doesn't add too much.
It's still a generalization.
What are we going to think about this
generalization?
Well, let's assume that
she's got a lot of friends.
So, she's checked a lot of people, she's
given a lot of people chocolate
and -- and they're all happy.
Well, is the premise true?
Well, do we believe
that every single person
that she gave chocolate to
was satisfied and happy?
I kind of tend to doubt that, Catriona,
sorry, but --
it's just, such uniformity is unusual
among human beings.
And so my bet is that a couple of them
didn't.
But notice that she didn't really need
that, because
she's only arguing that giving chocolate
will probably improve your mood,
not that it always will for everybody.
So she doesn't need that strong claim
about everybody.
So she's still on pretty firm ground with
regard to claiming that almost everybody,
or most of the people, have improved their
mood when she gave them chocolate.
We still might worry about a bias sample.
There might be some cultures out there,
or some types of people out there,
that don't like chocolate.
Maybe they're allergic to chocolate,
or something like that,
that would be really sad,
I'm sorry to even think about that,
it makes me sad.
But, there probably are, and they're
people that don't like chocolate.
And so, it's not going to work for them.
So maybe she wants to qualify her
conclusion a little bit, you know,
"among the groups that I've met:
different cultures might be different,
different biological conditions might make
people allergic to chocolate."
But, with regard to most of the people
she's met,
chocolate seems to work pretty well.
So we've got now a statistical
generalization:
"Most people, if you give them chocolate,
it improves their mood."
Great.
What does that show you about you, because
remember her conclusion is
that if you have chocolate, then that
chocolate will probably improve your mood.
So now she needs to take that
generalization
and apply it back down
to you as an individual,
to make a prediction about what'll happen
to you if you eat some chocolate.
So in this particular bit of evidence, she
needs to generalize up
to "most people will have their mood
improved
if they eat chocolate," and then back down
again.
And since that's true with most people,
and you're not special in any particular
way
-- or it would be a conflicting
reference class fallacy --
since you're not special
in any particular way,
the chocolate will also improve
your mood.
That's the way this first bit of evidence
seems to go.
So now we're ready for her second bit of
evidence.
Let's get all adjusted here
so that we can think about this new
bit of evidence that Catriona provides.
Okay, what she says is:
it could be that chocolate isn't really
causing the happiness.
Maybe they were just happy
before eating the chocolate.
Now, that's a problem.
If you're going to say that it improves
people's moods
when they eat chocolate,
it's not good enough
that people are already happy,
and then that makes' em want to eat
chocolate.
And so they eat chocolate to celebrate how
happy they are.
Well you gotta prove that it actually does
cause the improvement in the mood.
Okay, how are you going to do that?
Well, we looked, in the lectures on
induction, at causal reasoning.
What you need to do is manipulate.
You want to look at people who are not
happy
and see if the chocolate makes them
go up in mood
and manipulate the amount of chocolate,
manipulate how happy they are,
and see how those have effects
on each other.
And that's how you decide among the
hypotheses.
And that's exactly what
Catriona does.
"So I asked some unhappy people
whether they ever eat chocolate,
and they confirmed that they do,
precisely because it cheers them up."
Ah, so now we have a sample of people,
where we've manipulated their happiness.
We've looked at happy people and unhappy
people.
We've looked at people at times
when they're happy
and times when they're unhappy.
And then we can look at their chocolate
consumption
and we can check to make sure
that they're happier afterwards.
It's just like
checking whether smoking causes cancer.
We talked about that in the lectures on
induction.
If you want to know
whether smoking causes cancer,
what you do is you induce smoking
in creatures
-- in this case, lab monkeys --
that did not previously smoke
and see whether that increases
their cancer rate.
And what she's doing is she's saying:
"let's take people that
don't have happiness,
give them chocolate, and see
if that increases their happiness."
So she's using exactly the kind of
manipulation test
that we talked about
in the lectures on induction.
Good job, Catriona.
Now let's switch to the fourth bit of
evidence,
and I want to get ready for that one too.
Now, what Catriona says for her fourth
bit of evidence is:
"you may ask, what if all these people
are also in love,
and it's love that's making them happy,
not really chocolate?"
Because remember,
she doesn't want to claim
chocolate's the only thing
that makes you happy.
Love might be sufficient for happiness,
just like chocolate
also causes happiness.
How are we going to tell which one it is?
Well, in the lectures on causal
reasoning,
when we were looking at the tables,
and the diners who died
from the poisoned food,
one of the points that we made
was that if you have two candidates
for a sufficient condition,
you've gotta look at situations
where one of them is present
without the other and the other present
without the first one.
And that's exactly what Catriona does.
She says, I had to find people who eat
chocolate, but are not in love.
Whoa, well that's what
you're looking for,
because if you have some people
who eat chocolate,
but are not in love,
and some people who are not in love
but eat chocolate, you can test it.
And what did she find?
Well: "I did a mini-survey
outside my nearest corner shop,
and 80% if the people who confessed
that they were not in love
said they definitely felt their mood
improve when they ate chocolate.
Notice she's not claiming it's so
universal, 100% anymore,
she's down to 80%:
good move.
But in addition, she's now ruled out that
it's really the love
that's the only sufficient condition:
even when the love's not present,
you still get happiness
with eating chocolate.
So that's applying one of the tests that
we talked about
in the section on causal reasoning to test
for sufficient conditions.
Okay, we've done our bits of evidence one
and two and four.
We skipped over number three.
So what's your third bit of evidence?
Now, we've gotta look at that one.
Okay, what Catriona says is:
"I went to a chocolate factory
where all the workers
eat chocolate every day."
Not only that, it's free.
Free chocolate! Yeah, mm!
I love it.
"Like everyone else, these people could
theoretically be unhappy,
but they have smiles on their faces."
Wouldn't you?
Free chocolate all day long.
But wait a minute, wait a minute:
is this a good argument?
Like I said, it's a conclusion I like.
But we still gotta look at it critically.
Sorry, Catriona,
these people are happy,
but how do you know that they're happy
because of the chocolate, right?
They've got a job in the factory,
It's good having a job.
Chocolate's very popular, so maybe the
factory's doing really well,
which means they can pay them
more money, better benefits, good job:
maybe that's what's making them happy?
Sure, all these people in the factory
are happy.
But it might not be the chocolate.
It might be the fact
that they got a good job.
So I think this fourth bit of evidence is
not really all that strong.
Her number three, by the way:
the fourth one we considered.
It's not all that strong:
now, what does that show you?
You could say:
"Wait a minute, she's got four arguments,
one of them's no good,
so it all is back to nothing.
But of course, that's not
the right way to think about it.
She gave us four bits of evidence.
If one of them doesn't work,
and we've only got three left,
we've still got three left.
So if those first three bits of evidence
are good, and if they show at least
that it'll probably improve your mood,
and they establish
the cause of conclusion that she claimed,
then it seems to me
she's given us pretty good evidence for
the conclusion she was claiming.
And in doing so, she's exemplified a lot
of the different forms of reasoning
that we studied in the weeks
on inductive reasoning.
So, thank you very much, Catriona,
for submitting this wonderful video,
this wonderful argument.
We all learned from it
and we appreciate it.
Abbiamo ricevuto un esempio stupendo dei
tipi di transazioni che abbiamo studiato
durante le settimane dedicate
al ragionamento induttivo.
Abbiamo studiato le generalizzazioni, le
applicazioni di queste generalizzazioni,
come applicare questo al ragionamento causale,
con verifiche tramite manipolazioni
e con verifiche delle condizioni sufficienti.
Tutte queste cose vengono radunate
in un piccolo video stupendo.
Guardiamolo:
>> Ciao.
Mi chiamo Catriona e vivo in Svezia.
Per molti anni, ho mangiato
un pezzetto di cioccolato ogni giorno
e sono sempre stata fermamente convinta
che mangiare cioccolato rende più allegri.
In altre parole, la maggioranza
della gente sarà di miglior umore
dopo aver mangiato cioccolato,
che prima.
E vi darò quattro pezze d'appoggio
a sostegno della mia conclusione.
Prima pezza d'appoggio: ho incontrato
molte persone nel corso degli anni
e ogni volta che do loro un po' del mio
cioccolato, ne sembrano sempre felici.
Non mi viene in mente un solo caso
di qualcuno che mangia del cioccolato
senza sembrare soddisfatto dopo.
Seconda pezza d'appoggio: può darsi che
mangiare del cioccolato
non causi veramente la loro allegria:
sono semplicemente persone allegre
che mangiano del cioccolato.
Perciò ho chiesto a persone infelici
se mangiano mai del cioccolato.
E hanno confermato che ne mangiano,
proprio perché le tira sù.
Terza pezza d'appoggio:
Ho visitato una fabbrica di cioccolato dove
i lavoratori ne ricevono a gratis ogni giorno.
In teoria, essi potrebbe essere infelici
come tutti noi lo possiamo essere.
ma avevano tutti facce sorridenti,
con qualche sbaffo di cioccolato.
Quarta pezza d'appoggio: potreste chiedere
se queste persone sono anche innamorate
e se sia l'amore a renderle allegre,
e non il cioccolato.
Perciò dovevo trovare gente che mangia
cioccolato ma non è innamorata.
Ho fatto un mini-sondaggio al negozietto
vicino a casa mia,
e l'80% delle persone che hanno risposto
di non essere innamorate
hanno riferito che si sentivano
di umore nettamente migliore
quando mangiavano del cioccolato.
Perciò sembra davvero che
mangiare del cioccolato sia probabilmente
sufficiente per migliorare l'umore.
Ovviamente, c'è gente che non mangia
mai cioccolato ed é molto felice:
ad esempio, chi fa la dieta con successo
o il vostro dentista.
L'allegria può provenire dall'innamoramento
o da una promozione,
o dal raggiungere la cima dell'Everest, o
qualunque sia il vostro sogno più grande.
Però per una dose istantanea di allegria,
il cioccolato vi tirerà su -- mmmm.
>> Non era stupendo?
Sapevo già di amare il cioccolato
e che migliorava il mio umore,
perciò forse quell'argomentazione
mi ha convinto
perché credevo già nella conclusione.
Ed è lì che bisogna essere attenti.
Quando studiate un'argomentazione a sostegno
di una conclusione in cui credete già,
tenderete a pensare che è
un'ottima argomentazione.
Perciò se volete veramente sapere
se è o non è una buona argomentazione,
dovete esaminare attentamente quelle
che mirano a convincervi
di cose che già tendete inizialmente
a credere.
Perciò esaminiamo attentamente la sua conclusione.
La conclusione di Catriona era
molto cautamente ristretta.
Da una parte, diceva che il cioccolato
è una delle cose che ci rende allegri.
Non afferma che è la sola cosa
a renderci allegri:
L'amore ci può rendere allegri, scalare
l'Everest ci può rendere allegri,
tante cose diverse ci possono rendere allegri.
Lei afferma soltanto che il cioccolato
è una di queste cose.
Un'altra restrizione
sta nel fatto che lei dice
che il cioccolato
PROBABILMENTE ci tirerà su.
Non dice "certamente",
non dice che funziona sempre
o per tutti,
bensì che PROBABILMENTE, ci tirerà su:
perciò questo è un ragionamento induttivo
e lei non è tenuta a dimostrarlo oltre
ogni ombra di dubbio.
È una buona mossa in un'argomentazione,
perché è molto difficile dimostrare cose
oltre ogni ombra di dubbio.
Però c'è una parte della sua conclusione
che rende l'argomentazione difficile:
è quando lei dice
che il cioccolato ci tira su.
Questa è un'affermazione di causalità:
non è soltanto che mangiamo del cioccolato
e si dà il caso che siamo anche allegri;
è che mangiare del cioccolato ci rende
più allegri di prima,
cioè ci mette di miglior umore
di prima.
Perciò vediamo se le varie
pezze d'appoggio che presenta
davvero sostengono questa conclusione.
La prima pezza d'appoggio
fornita da Catriona è questa:
"ho incontrato molte persone
nel corso degli anni e ogni volta
che do loro un po' del mio
cioccolato, ne sembrano sempre felici."
Di quale tipo di argomento si tratta?
È una generalizzazione statistica
a partire da un campionario,
perché lei non ha incontrato
tutte le persone del mondo,
ha soltanto incontrato alcune persone.
Però nel campionario che ha potuto
controllare tutti amavano il cioccolato.
Lei aggiunge un'altra asserzione:
"Non mi viene in mente un solo caso
di qualcuno che mangia del cioccolato
senza sembrare soddisfatto dopo."
Beh, questo è un po' ripetitivo
perché lei dice che
non le viene in mente un solo caso.
Ha appena detto che ogni volta do loro
un po' del suo cioccolato, sono felici
e se sono felici,sono soddisfatti
perciò forse questo non aggiunge molto.
È sempre una generalizzazione.
Cosa pensare di questa generalizzazione?
Presumiamo che lei abbia molti amici.
Perciò lei ha controllato con molta gente,
ha dato del cioccolato a molta gente
e -- e sono tutti felici.
Orbene, è vera la premessa?
Crediamo che ogni singola persona
alla quale lei ha dato del cioccolato
è rimasta soddisfatta e felice?
Tendo a dubitarne, Catriona,
mi dispiace, però --
è soltanto che una tale uniformità
è inconsueta tra gli esseri umani.
Perciò scommetterei che non vale
per un paio di loro.
Però badate che non ha veramente bisogno
di questo, perché
sostiene soltanto che dare del cioccolato
probabilmente tirerà la persona su,
non che lo farà sempre con tutti.
Perciò non ha bisogno di
quell'affermazione forte su "tutti"
Quindi si è su un terreno piuttosto
solido nell'affermare che quasi tutti,
o la maggioranza, sono stati di umore
migliore quando ha dato loro del cioccolato.
Ci potrebbe tuttora preoccupare il rischio
di un campionario non rappresentativo.
Possono esserci culture là fuori
o tipi di gente la fuori,
che non amano il cioccolato.
Forse sono allergici al cioccolato
o qualcosa del genere:
sarebbe proprio triste,
mi dispiace soltanto l'idea,
mi rattrista.
Però esistono probabilmente persone
che non amano il cioccolato.
Perciò, non funzionerà con loro.
Quindi, forse lei dovrebbe restringere
un po' la sua conclusione:
"tra i gruppi che ho incontrato
-- altre culture potrebbero essere diverse,
altre condizioni biologiche potrebbero
rendere la gente allergica al cioccolato --"
Ma rispetto alla maggioranza della gente
che lei ha incontrato,
il cioccolato sembra funzionare
piuttosto bene.