Hidden objects question

[Eldrane]

Which skill do I need to develop to better discover hidden objects?

 

Does it matter which of my party has the skill or will the character with the highest level automatically be used regardless of who is the current party leader?

[Messier-31]

Mechanics.

 

Doesn't matter. The character with high mechanics needs to be in a close range to the hidden object in order to discover it (duh).

[Loren Tyr]

Usually you'll also need to be in stealth/scouting mode to detect them; though if a character has high enough mechanics skill (s)he can detect it even when not scouting.