Urgent help needed with bar puzzle

radman:

It certainly goes against instinctive logic

Next we are not really that logical, even when told that it is always better to swap people remain blind to the reality.

I bet there are more than a few instances where this flawed logic has found its way into computer programs.

I have know about this for years, and it still gets me. I can't help but think "but what if I chose right the first time?", even though the odds are against me.