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The big question for this segment is,
how trustworthy is a human brain as a problem solver and are humans rational?
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The question of human rationality has occupied the thoughts of some of
the worlds greatest thinkers.
For more than 2000 years.
Aristotle conceive the rationality was a fundamental characteristic of
human thinking.
For much of the 20th century,
economists assumed that decision making was underpinned by a kind of
universal rationality reflecting the maximization of personal expected utility.
These view is a sheen of human reasoning and judgment were governed by fundamental
principles that denote what good thinking should look like.
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On a more intuitive level,
people generally think that they know what good thinking is.
We have a strong sense of what a rational judgment looks like, and
can readily point out behavior that doesn't conform.
To our expectations for rational thought.
However, although you may consider your beliefs to be rational,
underpinned by evidence, knowledge and experience.
What about people who have different beliefs to you?
Are they irrational, mistaken, have poor judgment?
Are they less rational than you?
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Our judgments about the likelihood of a particular outcome are often biased, and
rely on simple heuristics, or
rules of thumb, that deliver solutions that are inconsistent with rational norms.
Our decision-making is typically influenced by the way in which problems
are described.
Features that are independent of the formal structure of the choice that we
are asked to make.
We will consider two classic examples of problems from the reasoning literature,
that depict the fallibility of the human brain in rational judgment.
And we will reflect on the implications of this work, for
our understanding of human rationality.
Let's start by considering a classic problem in the psychology of reasoning,
a problem first devised by Peter Wason in 1966.
The selection task is an ingenious problem that appears at least
superficially to be straightforward.
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Suppose you are presented with the uppermost side of the following
four cards.
Each card has a letter on one side, and a number on the other side.
You're also given a rule that governs what letter,
number combinations are acceptable.
The rule is, if there is a letter A on one side of the card,
then there is a number four on the other side of the card.
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Perhaps you thought that if you chose the A card and
there was a 4 in the other side, the rule would be true.
And if you chose the 4 card, and there was an A on the other side,
the rule would also be true.
What is interesting about this task is it looks simple, but
on average only 10% of people get it right, or give the logical response.
The logical solution is choose the A and the 7 card.
If you choose the A card and there is not a 4 on the other side, the rule is false.
Similarly, if you choose a 7 card which is not a 4, and
there is an A on the other side, the rule is also false.
What this task seems to demonstrate is that people do not
try to falsify the rule.
Instead they make selections that could only confirm the truth of the rule, but
never falsify it.
We will return at the end of the lecture to the question of whether this shows us
to be irrational or not.
As with most things in psychology, there is substantial debate about this.
But first, let's consider another way to some ingenious tasks.
A problem designed to examine scientific thinking.
Imagine you were told that there is a rule that governs acceptable three digit
sequences.
And your task is to discover what the rule is.
You are told that the following triplet conforms to the rule, 2, 4, 6.
In order to discover the rule you will have to generate number triplets.
And the experimenter will tell you whether they conform to the rule or not.
This is a really interesting task,
because it tells us something about how people test hypotheses.
For example, you might think the rule is an ascending sequence of
numbers separated by two, and you could test this by generating
triples such as 8, 10, 12 or 3, 5, 7.
Both of which conform to the rule of the experiment has in mind, but
it is not the same as your hypothesis.
The actual rule that the experiment has in mind is any ascending sequence.
What Wason found was that very few of his participants discovered the rule, and
the task became increasingly frustrating for many people.
But most interesting a study is the way people went about testing
their hypotheses.
They consistently generated sequences that conformed to the hypothesis they had in
mind, and hence they would invariably get positive feedback from the experimenter.
Typically, participants' hypotheses were much more specific than the general
rule of an ascending sequence.
Of course, the traditional scientific method as most scientists will tell you,
depends crucially on seeking avenues to disconfirm a hypothesis.
But Wason participants did this very rarely, and
hence did not successfully solve the problem.
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However, like any science, the psychology of thinking is characterized by debate,
disagreement, and conflicting evidence.
Many researchers, for example, would argue that the norms we use to evaluate
the quality of thinking, such as logic or decision theory, are not the right ones.
When thinking is evaluated against different norms,
it can often look perfectly rational.
Others have argued that testing positive instances of a rule can often be quite
adaptive, and deliver rapid problem solutions.
So, the debate continues, but
there was a clear lesson to be learned from this research.
If you're ever challenged in your views or your beliefs,
do consider all of the evidence available both positive and negative.
And always be willing to change your view in the light of disconfirmation.
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