Making Perception Checks Less Random

[Anthony]

Originally Posted by Vynticator

I think you're agreeing with me, fundamentally?

Only if you didn't mean what you said. Under controlled conditions, few skills are particularly random. It's just that controlled conditions are pretty rare for many skills.

[Anders]

Originally Posted by Anthony

Under controlled conditions, the difference between 'impossible' and 'automatic' is maybe a factor of 2 in size. The issue is that noticing things is hard and has an awful lot of possible distractions.

Yep. There are all kinds of biases and tricks that our consciousness does to us. Look at this video for instance and see if you see through it. Don't tell people about he solution, just tell us if you caught it or not...

Having 1 or 2 perception more than another person matters, if you are in the right section of the bell curve. The difference is largest in the middle, so if you target the TDM's to hit that sweet spot you will see a difference.

[vicky_molokh]

Originally Posted by Anders

Yep. There are all kinds of biases and tricks that our consciousness does to us. Look at this video for instance and see if you see through it. Don't tell people about he solution, just tell us if you caught it or not...

Having 1 or 2 perception more than another person matters, if you are in the right section of the bell curve. The difference is largest in the middle, so if you target the TDM's to hit that sweet spot you will see a difference.

Yeah, it probably doesn't get any more controlled than sitting in a room with no noises/events/etc. watching a video on your screen, only sound being that of the video in the headphones. (Okay, maybe there are ways to create more controlled conditions, but they're extremely unlikely outside a lab of some sort, and totally unlikely in an actual adventuring situation like spotting something during a campaign.)

[Vynticator]

Originally Posted by Anthony

Only if you didn't mean what you said. Under controlled conditions, few skills are particularly random. It's just that controlled conditions are pretty rare for many skills.

Um, yeah, like very rare indeed for Perception. That is what I wrote. Did you misunderstand or did you just want to throw the number out there about the 'factor of 2' and claim you were saying something new? It did sound terribly assertive and confident, well done.

And maybe less rare for tests of ST outside combat? Which, again, is what I said, and gave some examples which crop up in game situations.

[Anthony]

Originally Posted by vicky_molokh

Yeah, it probably doesn't get any more controlled than sitting in a room with no noises/events/etc. watching a video on your screen, only sound being that of the video in the headphones.

Sure it does. The major factor is the nature of what you're looking at, not your environment. For a simple example, consider reading something: as you move it further away, you will very rapidly go from "no problem" to "no chance".

Here's an example. Consider the following statements:

• I spotted him half a mile away.
• I only spotted him at ten yards.

Neither statement looks implausible. Now, let's start adding words:

• I spotted him half a mile away in front of me.
• I only spotted him at ten yards in front of me.

Still not that weird. Okay, let's add more:[list]

1. I spotted him half a mile away in front of me through heavy forest.
2. I only spotted him at ten yards in front of me through heavy forest.

or

1. I spotted him half a mile away in front of me across the salt flat.
2. I only spotted him at ten yards in front of me across the salt flat.

Suddenly statements (1) and (b) look highly implausible. The more you describe what's going on, the less random it all seems.

[vicky_molokh]

Originally Posted by Anthony

Sure it does. The major factor is the nature of what you're looking at, not your environment. For a simple example, consider reading something: as you move it further away, you will very rapidly go from "no problem" to "no chance".

Here's an example. Consider the following statements:
[ . . . examples . . . ]
Suddenly statements (1) and (b) look highly implausible. The more you describe what's going on, the less random it all seems.

The 'in front of me' makes lots of things misrepresented: if taken to mean that the target was directly in your FoV's focus and your mental focus when it was most relevant for your chance to detect it, it sorta implies having rolled two 1's. But people don't always focus on what they need to in order to notice it.
The linked video is a good demonstration:
People see everything, but only some notice the important things in the video, while others don't, even though everything's in plain sight right in front of them. That's the difference between sensing and perceiving, and the roll is largely to represent whether you perceive what you see (hear, touch, whatever).

Also, the forest example is totally off because it provides a flat penalty per unit of distance, not the standard logarithmic diminishing penalty.

[GodBeastX]

Guys, why do you have to roll all three dice? If you want it less random, just do: 7 + 1d6.

8 to 13 for dice roll result. No need to bring in fate and everything.

So you get a bit of random without horridly random, and it's still a 3d6 roll.

[Captain Joy]

Originally Posted by Anders

Yep. There are all kinds of biases and tricks that our consciousness does to us. Look at this video for instance and see if you see through it. Don't tell people about he solution, just tell us if you caught it or not...

The above does make a very compelling case for the roll-3d-under-target mechanic and the random element that it gives. However, I'm not convinced it should be applied to all, or even most, perception rolls that characters make in game.

Originally Posted by Anders

Having 1 or 2 perception more than another person matters, if you are in the right section of the bell curve. The difference is largest in the middle, so if you target the TDM's to hit that sweet spot you will see a difference.

The maximum bonus for being +1 Perception is 12.5%, +2 Perception is 25%. As an example, let's compare

• Adam with Hearing 10
• Beth with Hearing 12

Hearing a Sound: GURPS RAW, No Situational Modifer
Adam will hear it 50% of the time; Beth will hear it 74.07% of the time. In play, this will break down as follows:

37.03% both hear (50% x 74.07%)
12.96% neither hear (50% x 25.93%)
12.96% only Adam hears (50% x 25.93%)
37.03% only Beth hears (50% x 74.07%)

So, in this routine situation, when only one or the other hears (50% of the time), 25.92% of the time it will be Adam, or about 1 time in 4.

Hearing a Sound: GURPS RAW, -5 Situational Modifer
Adam will hear it 2.78% of the time; Beth will hear it 16.20% of the time. In play, this will break down as follows:

0.45% both hear (2.78% x 16.20%)
81.47% neither hear (97.22% x 83.80%)
2.33% only Adam hears (2.78% x 83.80%)
15.75% only Beth hears (97.22% x 16.20%)

So, in this demanding situation, when only one or the other hears (18.08% of the time), 12.89% of the time it will be Adam, or about 1 time in 7.

A 1 in 4 chance of Adam hearing something fairly obvious over Beth could be attributed to the "biases and tricks that our consciousness does to us". The 1 in 7 chance of hearing something not obvious could be modeling the fact that Adam is just less likely to notice it at all, regardless of biases and tricks of his consciousness.

Now let's see the results of using my 2 Fate dice house rule.

Hearing a Sound: 2 Fate Dice House Rule, No Situational Modifer
Adam will hear it 66.67% of the time: two fate dice will combine to give a <=0 result ⅔ of the time. So by my fate dice house rule, Adam's 10+(sum of the fate dice) will be less than his Hearing of 10 ⅔ of the time. Beth will hear it 100% of the time: the highest Beth can roll on 10+(sum of the fate dice) is 12, which is <= to her Hearing of 12. So Beth will never not hear it. In play, this will break down as follows:

66.67% both hear
0% neither hear
0% only Adam hears
33.33% only Beth hears

So, in this routine situation, when only one or the other hears (33.33% of the time), 0% of the time it will be Adam, so Adam never beats Beth.

Hearing a Sound: 2 Fate Dice House Rule, -5 Situational Modifer
A -5 situation modifier means even Beth is rolling against (her 12-5 which is) a 7. The best she can do on a 10+(sum of 2 fate dice) roll 10-2=8, so even she will never notice.

So, in this demanding situation, nobody notices the sound.

In play, I'm okay with neither or both noticing; it's the less perceptive PC beating out the more perceptive PC too often that bothers me. I guess I need to decide how often is too often.

Right now I'm thinking of going with this:

1. Actively notice with no distractions: "Turn it up to 11" rule (listening for any sound when it's quiet)
2. Actively notice with distractions: 2 fate dice house rule (listening for a specific name to be called in a noisy bar)
3. Passively notice without distractions: 2 fate dice house rule (rarely happens in play)
4. Passively notice with distractions: GURPS RAW (that bird's call is different from the rest)

I appreciate the effect of the "biases and tricks that our consciousness does to us". I think these signal to noise effects are two sides of a coin. For passive detection, it's seems pretty random. For active detection, what you're trying to detect is pretty much set by the physics of the situation, while noticing something else at the same time would be even more unlikely than the passive situation (a-la the -5 penalty that Single Minded [B85] characters get).

Additionally, you could use more (or fewer) fate dice to increase (or decrease) the standard deviation to suit the situation. (I suspect this is may be the whole point of the fate dice mechanic.)

[Say, it isn't that bad!]

To relate a relevant tale I heard somewhere (and may be apocryphal), some soldiers had received some beer from the locals. Naturally, rather than report anything, they wanted to make sure the sargeant didn't find out.

So they hid it.

Naturally, the sargeant found every single bottle. Until he got to one room. Looked under the bed, looked in the bed, looked in all the drawers, looked in the light fixtures, etc., finally gave up and left.

The bottle was sitting in plain sight on a side-table.

And, personally, I've missed things that were three feet from my nose. Basically? What you notice is filtered through your subconscious, and if you can tell what's going on in there, you probably qualify as Trained By A Master at minimum.

[ArchonShiva]

I think you're in the process of creating a fix that wiil add rules crud way out of proportion with the sum of both the problem's significance and the new rule's benefits. It also breaks down whenever the two characters involved aren't Alex and Beth (i.e. have Per scores other than 10 an 12).