Our system 2 tends to be a lazy guy. When prompted with an intuitive answer from system 1 to a problem, the default response from system 2 is to accept it.
In a series of relevant experiments, like stating how much a ball and a bat will cost if the bat cost 1 dollar more than the bat, and together they cost 1.10 dollars, we are shown how we tend to give the inuitive -and false- answer (the ball costs 10 cents) instead the right one (the ball costs 5 cents).
The main reason behind this situation is self control depletion. To pay attention implies some cognitive costs, and we need to exert our self control to keep ourselves focuses on a problem, instead of doing something else. But we seem to have only a certain amount of self control, and if it used in one task we won’t have any more energy to do the next task, as it is shown in several experiments, like the one in which the subjects have to resist the temptation to eat some delicious chocolate and then make a poorer performance solving a problem than the test group.
This seems to be literaly an energy problem as experiments have found a close correlation between lack of glucose and lack of self control.
One of these experiments turns out to be particularly gloomy. Judges that have to decide whether to give parole to a person in jail tend to give a lot more paroles after lunch, when their glucose levels were restored. It is not a beautiful picture for rationality to be shown how such an important thing as the freedom of a person depends on whether the judge has eaten lunch or not…
One can find in this chapter a very interesting discussion of what intelligence really entails, and Kahneman argues how besides our ability to make calculations and follow an argument, intelligence also implies the ability to bring to memory relevant data as well as the rationality to realize that an intuitive answer might be false and devote some cognitive effort to solve it properly.
To me the more relevant result of the chapter is this: when system 1 already considers that it has the right answer, it is very difficult to make the mandatory mental procedures to check whether this intuition is right or not. When we accept the conclusion as true, the argument turns out to be convicing even if it just a fallacy.
So far the content is convincing me. I have, however, one difficulty with the roses experiment:
All roses are flowers
Some flowers decay
ergo: some roses decay
This silogism is incorrect, and Kahneman presents the fact that most people will say it is true as an evidence of system 2 being lazy. I have to disagree in this case. In my opinion, the problem here is that our brains do not analyze logical problems using a formal system but a material one.
Let me revise briefly the famous experiment about formal conditionals. People were invited to solve the following problem:
There are three cards on a table: one depicts a circle, the second a square and the third a triangle. Next the following rule is presented:
If there is a circle in one side, then there will be a square in the other side
And subjects are invited to rise the minimum amount of cards necesary to check if the rule is true or not.
Everybody rises the card with the circle, which is correct, but most of them also rises the card with the square, which is not needed at all. Whether there is a circle or not the rule still holds. instead, very few people rises the triangle, which is mandatory. If there were a circle in the other side the rule would have been proved false.
However, if you do the experiment with meaingful objects and rules (like say, people keeping or not keeping a promise) almost everybody solves the problem.
So, my suspicion of how the roses experiment could be pointing to another direction. The reason we fail and see the silogism as correct is because we know that all flowers decay and roses decay as well, and we treat logic from a material point of view, and we see the argument as correct.