Prisoners' Dilema

Question

I started to learn about game theory just now. I am confused about the prisoners' dilema, when 2 prisoners are given a choice whether to keep silent or rat out the other guy. From what I read, if one rats out the other and the other guy keeps silent, then the ratted out guy will go free, while the other guy serves 10 yrs in prison. But, if they both rat out each other, then they both serve 7 yrs. See more details here: Prisoners' dilema. From what I read, each guy will be confused as to whether he should choose to rat out his friend or not - he wants to be free, but he is also afraid if the other guy rats out him, then both of them will not serve the shortest punishment.

Now the question is :

is all of this payoff-matrix is given to both prisoners? if so, it's just a simple answer, both of prisoners will choose to keep silent (so both of them will serves 2 yrs in jail), why? (because they will think if they rat out other guy, how if others rat out him too? both of them will serves 7 yrs in jail). I know this Prisoners' dilema gives more details than I thought, but maybe I get the wrong idea of this?

Updated : sir, I found an interesting thing after a few discussion with "myself". The dilema that I found from this case, "may" be :

1. if I rat him out, I may be get free, but how if he rat me too? both of us will serves 7 yrs. (1st dilema)
2. if I am confessing, hmmm I serves 2 yrs at least not as long as 7 yrs, but omg, he'll get the chances to rat me out, so I will get 10 yrs in jail while he get free, I wont make him happy for this (2nd dilema)
3. so, what is the best choice for me? (3rd dilema)

better ratting him out or confessing? hmm, if I rat him out, I will get 2 chances (free or same punishment 7 yrs), but if I confess, I will get 2 chances also (same punishment 2 yrs or 10 yrs while others will free, I wont give him a chance to be free). I know!! the best choice is better ratting him out, yeah!!! omg, but it means I wont be free, cause I know he'll think the same too, it will end up both of us ratting each other (7 yrs of jail), haha I know he'll choose to rat me out cause of this, I better to choose to rat him out too. (both of us end up 7 yrs)

so I think in this case 1st and 2nd dilema will lead each guy to the 3rd dilema, which is lead to the conclusion to choose rat each other, and end up 7 yrs.

so I will updated my question to :

are these dilema which mentioned by "Prisoners' dilema" ? if so, it's so easy to end up in the equilibrium state (ignore the 7 yrs or 2 yrs in jail, just called it "same punishment").

Answer 1

Prisoners' dilemma is an example of Nash equilibrium, in which (1) each player of a game knows the payoff from each of his moves, given the other players' moves. In other words, all players know the payoff matrix. And (2) each player of the game plays a "best response" - a well-defined term. Basically means you play to maximize your own payoff, given all other players' moves. See Rubenstein's book on game theory for a reasonably accessible explanation.

Answer 2

Each prisoner is given the table of payoffs, but neither is allowed to know what the other one has answered. Therefore, because prisoner Alice can reason that, if prisoner Bob guesses that Alice will be silent, then Bob will rat, thereby gaining the best outcome for himself, and the worst outcome for Alice. Bob will reason the same way. Therefore, neither one of them will stay silent, and both will rat, ironically ending up with a bad result for both of them. But both ratting is the Nash equilibrium, where if one changes his/her position (while the other one stays fixed), he/she will only worsen his/her situation.