Re: Psychic Signatures
 

You might be right.

But I know the number and kinds of things I'd be willing to risk getting heard or seen doing or saying in a 100 yard radius (+10), especially in a pinch, are much greater than the number of things I'd be willing to risk getting heard or seen doing or saying in a 2.5 mile radius (+20).

And this ignores the fact that psychic signatures aren't like mundane signatures. Not everyone can notice them. In a world where there are maybe 50 psis, all capable of Psi Sense, living in a given large metropolitan area, my odds of not getting "heard" in a 100 yard radius are a lot better than not being heard in a 2.5 mile radius. I'd risk the +10 much more often than I'd ever risk the +20.

EDIT: I'd also like to point out that for each +1 on the Size and Speed/Range Table there are increasingly large gaps in distance. To me this covers entirely the possible "diminishing marginal cost" of "loud" powers.

Re: Psychic Signatures
 

In a world with supernatural abilities, the onus is still on the person with the supernatural ability to cough up the points. Joe Catburgler doesn't suddenly develop a disadvantage "Noisy Catburglary" because someone else on Earth buys the ability Detect Catburglary (Reflexive, Reliable +40) and Warp (Accessability: only to sites Detected with Active Catburglary).

Except possibly Enemy, if Anti-Catburglar-Man then takes it upon himself to teleport to the location of every act of catburglary to blow an airhorn or something.

This is one of the reasons why your Nuisance Effect: "really noisy psychic signature" is probably worth less than a comparable visible or audio signal - but as a GM I'd suggest that, for the same price as regular audio-visual noisiness, the alternative that it's so "noisy" that even the non-psychics get a psychic "ping" about you.

Re: Psychic Signatures
 

If we assume that only 50 individuals in the city can even detect your "High Signature" power, then it should be worth next to nothing. A gunshot on a crowded street (ie, "normal" signature for an Innate Attack) could be heard by scores or hundreds of people. A psychic signature would need to cover the entire city to be similarly "noticeable" if psychics are that rare.

Re: Psychic Signatures
 

A few psis that might "hear" you out of a possible 50, depending on their abilities and power levels, could be a lot more dangerous to you than scores of mundanes hearing you firing a gun (or the psi equivalent). They can affect you from a distance with their powers, you won't know what powers they can bring to bear against you, they might be able to get to you faster (Warp or super-speed or Projection), possibly harm your ability to use your power or undo what you've done afterwards, or they can use remote senses to "keep their eye on you" after you've caught their attention (in which case your privacy is shot to hell). And that doesn't even cover the possibility of randomly placed government psi-detectors placed secretly throughout the city.

Re: Psychic Signatures
 

If you discharge a firearm indiscriminately within city limits (especially in view of others) you'll soon have law enforcement or even the military breathing down your neck. Basically, my point is that High/Low Signature shouldn't be worth more points for something that fewer people can detect, even if those few people may be powerful and dangerous.

Anyways, I think I'll follow the good Reverend's suggestion of -5%/-10% for a +10/+20 to detect.

Re: Psychic Signatures
 

I don't think it's about "number of people who can detect", it's about how often your use of your powers will be detected, and maybe most importantly, how often you'll stop and think "hmmm... maybe I shouldn't use my power, stealth and subtlety are what's needed now, not signatures every psi in a 5 mile radius can detect".

But to each his own. I'm going to go with -5% per +2 because there's symmetry in that, and because it leaves the scale open-ended, and in the setting I'm planning it'll be important to operate with a soft touch.

I take and agree with RPK's point that not everything in GURPS can be mirrored on the other side (disadvantages and limitations costing the same as their advantage and enhancement analogues often may not work or be balanced), but I personally think this is not one of those times. I don't just believe that because it feels right to me, but because the ranges associated with the penalties to Sense rolls grow wildly as they progress; if they grew linearly I might be a lot more inclined to agree but I feel the chart's progression is justification enough for my position. The difference between 0 penalty and -1 penalty is only a yard, whereas the difference between a -10 penalty and a -11 penalty is 50 yards, for instance, and Low Signature levels really only stop people from noticing anything if they're right on top of the situation at ground zero. I'm honestly kind of confused by the brilliant focus and attention to detail put into things like Psi Sense, Signature Sniffer, Hide Signature, et al, if for the most part, it's all for rather short range effects that you have to be actively looking for.

Re: Psychic Signatures
 

It occurs to me that magical powers might also have signatures. Those attuned to magical signatures might, for example, find that a place "reeks of demon" based on its magical signature. If an individual mage becomes well-known enough his own magical signature may be recognizable so that attuned people know whether he cast that spell or whether he has cast a spell in the vacinity.

Of course, most mages are not well-known enough that just anybody attuned to magic can recognize their auras. It would usually require acute personal experience with that mage, as an ally or an enemy. (Demons are a different story -- you could usually tell there were demons around without having to know what specific demon it is).

Re: Psychic Signatures
 

From my reading of the Low or No Signature section on p. P103, I've always assumed that each kind of power source leaves "psychic signatures", traces that can be detected via a sense like Detect Signatures of This Source (or abilities like that). I certainly agree magic (it's specifically mentioned) will do that, but I think any power source that doesn't have No Psychic Signature: Undetectable +25% built into it will leave traces behind. I know using the word "psychic" feels more for psis, but really I think it's a generic enough term (and it is the official term as per Psionic Powers, p. 20) - after all, it's not "psionic signature". In any event, I agree with you and I think for mages having high psychic signature magic would be just as bad, if not much worse, as it is for psis.

You could always put levels of either to increase or decrease the signature of Magery so all your spells leave less of a trace behind.

Re: Psychic Signatures
 

While I'm generally leery of attaching modifiers to Magery that affect the properties of spells (rather than access to spells or casting method) in this case I like it.

The only other way I can think of to do this would be using the rules to add Enhancements to spells (Thaum p39). Hence, attaching No Psychic (or Magical) Signature to a spell would penalize the casting by -5. That seems kinda steep... but maybe it's appropriate.

Re: Psychic Signatures
 

Huh - I hadn't seen that rule in Thaum, thanks. It certainly is less of a blunt force instrument than adding it onto Magery.

Is there an official stance on adding general modifiers to Magery to affect the properties of spells? I can definitely see the need to be leery - and certainly nothing grossly abusive like "Reduced Time" or "Extended Duration" should be applied, I should think.