Saeviomagy said:
At present, I understand your position to be
1. PC's get a sense motive roll when I feel like it, not when it's important.
2. Social skills are optional. A strong roleplayer can cope without them, and a weak roleplayer will get very limited use from them.
3. Somehow the same would apply to swimming. If I wanted to be flippant, I'd also assume that you require your players to go for a couple of laps in a pool or something every time their character fell in water, but I'm pretty sure both of us would agree that's a ridiculous situation. I'll assume instead that you mean that swim checks are called for when you feel like it. Again, if I wanted to be flippant, I'd assume that if you didn't feel like it, your PC's would drown, and again I'm pretty sure this isn't the case. So that's a second point on which they're unlike social skill rolls in your game.
If this isn't your position, please clarify it.
Sure.
If you read the Checks Without Rolls section, Take 10 is an optional character choice. If you read the DMG, players are encouraged to Take 10.
But, what about the case where players do not know the DM is rolling a Sense Motive for them? Can they choose to Take 10? Obviously not. So, can the DM choose to Take 10 for them?
I think so. If not according to the rules, than according to rule zero.
And, the DM can obviously choose Take 10 for the NPCs. Now, the interesting thing about social skills is that there is little in the way of distraction or threatening in them for most situations (with the exception of Intimidation). Hence, most of the time, you can Take 10 (both PC and NPC).
And according to the DMG:
"For example, you can decide that the task is practically impossible and modify the roll or DC by 20. Feel free to modify these numbers as you see fit, using modifiers from 2 to 20."
Now, I just verbosely explained all of this for a reason. The reason is that the rules allow the DM to make the opposed check and the DM decides the modifiers, whether the dice are rolled, and whether Take 10s are performed. In other words, the DM can decide the outcome based on the situation, sometimes regardless of whether he rolls the dice.
Now, before you start in again with your "Screwing the players" mantra, what I am talking about here (in the case of Sense Motive / Bluff) is that most of the time, a mildly lying NPC (or PC for that matter, we have yet to discuss when the shoe is on the other foot) is not going to be caught unless he starts contradicting himself or unless he starts making outrageous claims or unless the PC's skill total is significantly higher than the NPC's.
But, this philosophy (that little white lies or omissions are typically hard to catch) is the antithesis of a game system where D20+x is greater than D20+x 50% of the time. 25% to 75% of the time, if you roll the dice, you have to tell the PC that the guy is being evasive or some such (if you are not going to be truthful to your players about this, why bother to roll the dice?). I, as DM, think that is WAY too high of a percentage. 10% to 15% seems more reasonable to me, but rolling dice won't get you into that range (unless you explicitly only make the roll a success on 18+ as opposed to actually figuring out reasonable modifiers).
So, when do you throw the dice and get into that huge 25% to 75% range?
1) When the player asks (i.e. it is important to the player).
2) When the DM deems it important to the storyline.
3) When the NPC says something outrageous that is hard to believe.
4) When the PC(s) appear to be suspcious of the NPC.
But, I do not do this for every lie because I do not think most lies would get caught without a lot of additional information to indicate that they are lies. In fact, suspicious PCs should occassionally incorrectly "sense" an NPC is lying when he is not.
So, I typically roll Sense Motive / Bluff when one or more of the four conditions above apply. I might even do it if the NPC contradicts himself, but to me, that is part of the fun of roleplaying and my players should have more fun noticing that kind of thing on their own as opposed to me spoon feeding it to them with a dice roll, so unless it is critical to the storyline, if I throw in a contradiction, the players either pick it up or not on their own.
I blow off rolling Sense Motive / Bluff the rest of the time, just like I blow off roleplaying going to the latrine.
Now, let's go back to the other foot. If a PC is lying to an NPC (and the DM is unaware of it for some reason), should the player tell the DM he is lying in order for the DM to roll Sense Motive / Bluff? Or, should he roleplay it out and not influence the DM's roleplaying of the NPC? Which typically results in more fun?
And now, turn this back around. Which is typically more fun (and more conducive to better roleplaying) for the players, when they are told that an opponent is lying, or when they figure it out for themselves?