If P, then Q. P. Therefore, Q.
If P, then Q. Not Q. Therefore, not P.
Detecting Cheaters has been on my "to read" list for quite some time now, but only got around to reading it a few days ago. I found it quite interesting, so going to give a rehash of it :)
Some of you may recognise the above as a 'logic statement', and to some extent it is fairly obvious. Associating the above with a concrete example may make things easier to understand.
If you forgot your keys, then you need to call the locksmith.
So in the example above, P='forgot your keys', and Q='call the locksmith'. Does that all makes sense so far? Let me introduce what is known as the Wason selection task. The concept behind this task is quite simple - you are shown four cards, each containing some form of information on each side (eg. one side will be about forgetting/remembering your keys, the other about the locksmith). The cards are placed so you see (face-up):
- (a) Forgot keys
- (b) Remembered keys
- (c) Need to call locksmith
- (d) Don't need to call locksmith
Your task is simple, determine which two cards you need to flip in order to confirm that the "If you forgot your keys, then you need to call the locksmith" statement is true.
So, which did you choose, (a) and (c)? If you did, then you're wrong, but don't worry, you're not alone. (a) is correct. You need to check that if you forgot your keys, the other side of the card says "need to call locksmith".
However, (c) is incorrect. The above statement puts no restriction on "you needed to call a locksmith, because of something", 'something' can technically be anything and the above statement still holds true.
The correct answer is (a) and (d). In order to confirm the above logic statement, you need to make sure (a) is true, and (d) is true. (a) as aforementioned, and (d) because you need to check, if you didn't need to call the locksmith, then you didn't forget your keys; if the flip side of that card had 'forgot your keys' then it goes against the "If P, then Q" statement. In other words:
You forgot your keys. Therefore, you need to call the locksmith.
You don't need to call the locksmith. Therefore, you didn't forget your keys
Confused? Let's try again...
If you ate dessert, then you ate your vegetables.
So, how do you confirm this statement? How do you make sure that if your little sister is eating that delicious chocolate tiramisu, she ate her brocoli? Again you have four cards to choose from (I'll mix up the options a bit, and don't cheat by comparing with the above!):
- (a) Ate dessert
- (b) Ate vegetables
- (c) Didn't eat dessert
- (d) Didn't eat vegetables
Which two would you choose? If you were like me when I first read Schneier's post the answer might've just 'lept' out at you, (a) and (d). You want to make sure if your sister (a) ate dessert, she really did eat her vegetables; and that if she (d) didn't eat her vegetables she shouldn't be eating dessert! Now, did you get that right? or at least was that easier to understand?
If I explained things properly, then you really should've found the latter example much easier to digest. The reason appears to stem from the fact that the latter example is related to cheating. We seem to be more adept at figuring out if someone 'cheated', for example, if they ate dessert without eating their vegetables, compared to figuring out if someone called a locksmith or not because they forgot their keys.
What strikes me here, is that without any "training" we can easily distinguish one scenario from another, when logically they are equal. This seems to mean that we are designed to be able to pick out when someone is getting something they don't deserve or haven't earnt, I guess you can say we're all designed to keep the playing field fair. Interesting thing is, as far as I know this isn't the only thing we're hard-wired with. I remember in psychology, we learnt that humans can be taught to fear spiders more easily than say, a wooden chair. So somehow we learn to fear things that are potentially more dangerous to us more easily. Evolutionarily, this all makes sense. Making sure someone doesn't get all the benefits without doing the work. Making sure that we quickly learn to 'fear' what may potentially kill us. Though that makes me wonder, how many other things are we, as humans more prone to being able to accomplish, learn and execute?