Do you know when you fail a saving throw?

Question

The pathfinder rules say:

A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack. Likewise, if a creature’s saving throw succeeds against a targeted spell, you sense that the spell has failed. You do not sense when creatures succeed on saves against effect and area spells.

If a creature's saving throw fails against a spell, does the creature still feel that "hostile force or a tingle" or otherwise know that they've failed a save?

(I'm asking this question because it's relevant to How powerful can a 20th-level Wizard make a 1st-level Fighter without allowing him to realize it is the Wizard's doing?)

Answer 1

No rule indicates that you sense when you have failed a Save against effects that cause no apparent change. In fact, the rule you quote seems to imply that you don't.

This is necessary for many spells, such as Enchantment spells, to make sense... if you feel a hostile force taking over your brain every time you're affected by Charm Person, you might stop having tea parties with whatever creature was trying to be your friend. Also, knowing you failed a Save after interacting with an Illusion is exceptionally telling.