For example, an opponent has overcalled 2 Clubs and we need to figure out whether they hold
The decision is not entirely logical yet it is not completely random either.
What usually happens after the post-mortem, however, is that the person in the hot seat, their partner and anyone else who knows the full hand concludes that "he should have got that one right."
For now, we are no longer grappling with the issue of assigning appropriate weights to all the subtle inferences. Subconsciously, either in an apologetic attempt at treating bridge as a purely logical pursuit or in an indulgent ego stroke for the capacity of our powers of deduction, we tend to favour the succesful choice. The weights that we struggled to appropriately apply to various factors at the table now appear to be clearer.
There is a term for this phenomenon, hindsight bias, that I came across in this brilliant book. Some links for the author and detail of his work can be found here, here and here.
Meanwhile, back on the subject, try solving a defensive problem
Trick one goes spade queen ducked all round. Trick two is a spade to the king ducked again leaving us on play. Is there a clue or will we eventually succumb to the hindsight bias ?