[Basic] Advantage of the Week (#40): Discriminatory Senses, Sensitive Touch

[whswhs]

Originally Posted by Anthony

That's just a good perception roll.

But there are different ways to get a good perception roll. You can have a sense with high bandwidth, like the human eye. You can also have a brain that's good at processing information and extracting meaning from sense data.

[evileeyore]

Originally Posted by Refplace

It is not just about memorization tricks though.
Profiling is pretty much Memorizing but Discriminatory seems more about sensing enough detail to see and recognize individual differences. That helps you remember but is really about the level of detail.

Which is why I'd say Humans have Discriminatory Sight and Discriminatory Hearing.

Originally Posted by whswhs

You can also have a brain that's good at processing information and extracting meaning from sense data.

And the human brain is not normally wired for scent analysis the way a bloodhound, bear, or mole is.

Not an argument, a statement of support for Discriminatory Smell being an advantage most humans do not have.

[Anthony]

Originally Posted by whswhs

But there are different ways to get a good perception roll. You can have a sense with high bandwidth, like the human eye. You can also have a brain that's good at processing information and extracting meaning from sense data.

While this is a realistic distinction to make (20:20 vision with Per 10 and 20:40 vision with Per 12 should be distinguishable), it's really not one GURPS normally chooses to make: either something is impossible, or it's got a difficulty modifier, and if it has a difficulty modifier, all you need is more plusses. Distinguishing people by scent is something humans can do, just extremely unreliably, so it's a difficulty modifier.

[vicky_molokh]

Originally Posted by Anthony

If the paints are different types (say, lead-based vs latex) an educated human palate could probably tell. If not, animals generally aren't going to be able to tell the difference either, though animals noted for their sense of smell are likely to be somewhere around +10 relative to humans.

I am talking about the two paints containing two different chemicals used for the pigment, with Discriminatory chemoreceptors being able to distinguish them and non-discriminatory ones signalling them to the CNS as interchangeable.

Originally Posted by Anthony

The problem is that discriminatory is vastly overpriced for a mere +4 bonus. What do the other 7 points account for?

The intent seems to be for the ability to detect certain things that cannot be detected by a mere Sense-with-a-4-penalty. The only problem is the size limits of books and research means that giving examples is difficult.

Here's a list of examples from another roleplaying games and novels:

• The character can recognize others and hints of their recent activities by smell (duh).
• He can track by scent alone (without using vision at all).
• With a legendary success, he can detect but not identify a few drops of tasteless poison in a wine—as its presence serves to dilute the [taste of the] wine.
• In Echopraxia, a character listens for sound signatures in peoples' hearing to estimate how long ago those people had a (stressful) encounter with her racemates (which is usually stressful for humans).

[Anthony]

Originally Posted by vicky_molokh

Here's a list of examples from another roleplaying games and novels:

The first three of those seem like extreme difficulty modifiers. The last doesn't seem like something discriminatory sense would let you do, it appears to be sense-based mind probe.

[vicky_molokh]

Originally Posted by Anthony

The first three of those seem like extreme difficulty modifiers.

If you believe that humans should be allowed such rolls at extreme TDMs.
If you subscribe to such a view, I may as well tailor the wording for such a view: "Discriminatory Sense only provide a +4 Acute Sense equivalent, but allows one to disregard many extreme negative TDMs". With the problem being that a list of examples would take up an official PDF of its own (which I'd buy had it existed!).

Originally Posted by Anthony

The last doesn't seem like something discriminatory sense would let you do, it appears to be sense-based mind probe.

Only as much as Diagnosis and Psychology are mind probe and Detect (Life, Analyzing), i.e. not really. What it does is allows you to use your Hearing to gather the necessary data for the analysis.

[whswhs]

Originally Posted by Anthony

While this is a realistic distinction to make (20:20 vision with Per 10 and 20:40 vision with Per 12 should be distinguishable), it's really not one GURPS normally chooses to make: either something is impossible, or it's got a difficulty modifier, and if it has a difficulty modifier, all you need is more plusses. Distinguishing people by scent is something humans can do, just extremely unreliably, so it's a difficulty modifier.

This kind of thinking is hard for us to do, because we are trying to imagine the things that our senses simply can't detect at all, but that the senses of other species can. But those other species can't talk to us about how they perceive the world, so we have to infer such things indirectly; and that information isn't a matter of common knowledge for us.

But let's try doing it the other way round. We do have Discriminatory Vision. What is it like to have mammal vision rather than primate vision?

Primate vision involves having a high density of cells in the fovea; a cat or dog has much less, and has about 1/10 the angular resolution. This is about like 20/200 vision. There are actual people whose corrected vision is no better than 20/200. This has a common name in everyday language: legally blind—20/200 is the threshold of legal blindness. (And even there, they mostly have optical blurring rather than sparse innervation.)

With that low resolution, to begin with, you can't see facial expressions, except for the rather gross ones that are symbolized by emoticons. Primate faces have a lot of small muscles that form small expressions, and that makes up a lot of our social signalling. An average mammal can't read those subtle facial signals. "The frown, and wrinkled lip, and sneer of cold command" don't register. And so dog and cat faces just don't have the fine motor control to make all those expressions, because there's no payoff.

There's also the ability to read. All of our reading is done with the fovea; reading is scanning the fovea across a page. Mammal vision might let you resolve the gross shape of a single letter on a page, if it were in large print, but it wouldn't let you take in a whole word, or the subtle complexity of a kanji. You might at best be able to get up to Broken literacy with mammal vision.

The Discriminatory senses let you recognize individuals. Mammal vision probably gives you a poor and unreliable recognition, if any. Your dog knows you by your scent, or the sound of your voice. (Conversely, your dog knows which other dog has urinated on a lamppost or rock, and how recently; you probably can't get beyond "this smells like pee!")

My current cat is very visual, for a cat. He loves to look out the window, especially if there are birds outside; I've seen him play with a tablet screen tuned to a channel that display fish or mice; he's very good at catching or tracking a thrown toy. But sometimes he gets to the area I threw it to and has trouble finding it, because it's small and doesn't stand out if it's not moving. And he can't see my facial expressions. He has Acute Vision for a cat, but he doesn't have the equivalent of human eyesight and never will.

Now turn that around, and apply it to a different sense. It's tricky to narrate "your character routinely perceives things that you and I can't notice," and the GURPS rules for Discriminatory senses are kind of handwavy. But that's what they're pointing at.

[whswhs]

Originally Posted by vicky_molokh

If you believe that humans should be allowed such rolls at extreme TDMs.
If you subscribe to such a view, I may as well tailor the wording for such a view: "Discriminatory Sense only provide a +4 Acute Sense equivalent, but allows one to disregard many extreme negative TDMs". With the problem being that a list of examples would take up an official PDF of its own (which I'd buy had it existed!).

I've scanned through Enhanced Senses, and it doesn't go into that much detail. But one thing it says is that if you have Sensitive Touch, you are exempt from "work by touch" penalties for skills. You have a familiarity penalty for the first 8 hours using a new skill that way—but if you had a race with Sensitive Touch, they probably would routinely learn skills that way and be over the familiarity penalty as soon as they had the skill. So that's a -5 difficulty modifier being dropped.

GURPS is kind of ambiguous about this. Discriminatory senses give +4 to do something, which is a big modifier; it's the same as the "miraculous aid" modifier for Abilities Affecting Skills. But Analyzing on Detect just says that the basic roll to analyze automatically succeeds, and the really hard analysis is possible on a normal success. That might be a way to look at this.

[Flyndaran]

Originally Posted by Anthony

While this is a realistic distinction to make (20:20 vision with Per 10 and 20:40 vision with Per 12 should be distinguishable), it's really not one GURPS normally chooses to make: either something is impossible, or it's got a difficulty modifier, and if it has a difficulty modifier, all you need is more plusses. Distinguishing people by scent is something humans can do, just extremely unreliably, so it's a difficulty modifier.

Most people are unreliable identifying others by scent alone. But some find it as easy as identifying people by voice alone. What kind of penalty would that involve such that those like my family could just do it on normal rolls?

[whswhs]

Originally Posted by Flyndaran

Most people are unreliable identifying others by scent alone. But some find it as easy as identifying people by voice alone. What kind of penalty would that involve such that those like my family could just do it on normal rolls?

This is the first I recall hearing of your family having this ability. But from all your past mentions of it, I must say that I don't really feel sure exactly what it is you can do. And I'm not entirely sure that you know, either. You haven't undergone double blind testing, right? At best what you're saying is anecdotal. I did some looking for studies of animal and human chemical senses, and I really couldn't find anything detailed, so I don't think what you have to say is greatly worse than what GURPS is based on, but I'm not entirely sure how to deal with it.

However, I think there are several ways to deal with this, based on wanting to create a GURPS character who can do what you suppose you can do:

* We give most people a penalty, and give you a lot of Acute Smell or a high Perception

* We give most people a penalty, and let you take Discriminatory Smell, perhaps with Special Exercises or even Unusual Background to explain it, or perhaps not

* We say that most people can't even attempt the roll, but that you can, and that this is because you have Discriminatory Smell

(Incidentally, it occurs to me that a big question is how often you can actually do this stuff. You know when you register an odor and you may be able to find out if the odor is actually there. But if you fail to register an odor, is there a process you go through to find out if it's there and passed you by? If not, you don't know your success percentage, so you don't know if you're rolling vs. a 6 or a 16.)