What is the difference between good and bad reasoning?

Some concrete examples

Let’s take a claim:

If there is a cat on the mat then there is a fish in the fish bowl.

Let’s also take the evidence:

There is a cat on the mat.

Consider the conclusion:

There is a fish in the fish bowl

And what the data show is that most people readily agree that the conclusion is valid.

It’s the same kind of logical reasoning that underpins the Harry example discussed by Rob in the video.

However, let’s take the same claim:

If there is a cat on the mat then there is a fish in the fish bowl.

And take some different evidence:

There is not a fish in the fish bowl.

Now consider the following conclusion:

There is no cat on the mat.

This time the data show that some people struggle to see that this conclusion is valid.

Human reasoning therefore can appear a little quirky.

Some valid arguments are readily understood others are not.

Time for you get thinking

As the material this week unfolds you must bear in mind several things. First unless you are genius, a real genius, then you will tend to be tripped up by some of the puzzles we present. However, if you do manage to reason logically about everything we present then that will be exceptional. It is, therefore, best to be prepared for the fact that, in some cases, you will be shown to reason irrationally. This is not exceptional – sometimes a few people err, and sometimes most people err.

What we as cognitive psychologists are trying to do is understand how and why people make errors in their reasoning. If we can understand this then we can take steps to try and help them avoid similar errors in future.

Ok let’s get started…

Here’s a claim:

If it’s raining, I get wet.

Now some evidence:

I get wet.

Is it therefore valid to conclude that:

It’s raining??

Alert

The answer is provided in the next step so before moving on work out what you conclude.