You also have not answered my point that someone who takes four years to learn material others learn in one has below average learning ability.
That's because in Dwarf Fortress, you can't be any worse than anyone else at learning if you've had as much practice as everyone else. Having to redo the year over and over would make you better at learning than anyone else.
Baloney. Someone spending four years to learn the material others learn in one is
manifestly below average in learning ability, and as such
needs that extra experience
just to get to the same level of ability as everyone else. He's not even at parity with those peers unless and until he can learn as fast as them. On a DF scale, he as
negative skill in learning.
So gobbos and kobalds have cloaking devices, huh? Honest-to-goodness cloaking devices that only fail if you run headlong into them? That's not an abstraction?
Just saying, don't talk of what the spotting skill does (without addressing the fact that having sharp senses does not contribute) if it doesn't actually take place and isn't even remotely plausible of an abstraction. If stealth is not actually stealth but invisibility, then we shouldn't pretend it's anything else just to justify a redundant skill that seems to go up by simply seeing someone, whether they're sneaking or not. Ridiculously poor abstractions should be kept out. If you want to pretend stealth makes sense, might as well cut the middle man and tie detection to actual senses instead of having to bang your head to a wall when your sentry lets a kobold past him because his detection skills failed to spot the kobold walking across a bridge.
And what makes you think that each z-level is completely level ground, that grass is as short as a lawn, and that a kobold sticks out like a sore thumb against the background from afar? It's an unfathomable assumption in the real world. In that world (the one you live in), there are plenty of places to hide in a 'flat' plain. A real grassland is nothing like a lawn, and rocky terrain will afford plenty of places to hide. Also, your dwarves are not omniscient — your lookout doesn't necessarily know that the person he sees on the bridge is a dwarf or a kobold. Also, if he's a lookout, he's not going to be looking exclusively at one bridge.
Again, the skill starts at 0. You're blind as a bat without practice. Practice seemingly being just seeing enemies. I guess my guards that have never killed a goblin just figured the child snatcher wearing someone was a real dwarf and let him pass. But not to worry, their eyes will surely be honed for some reason when they stab someone a few thousand times and see their faces while they do so.
Strawman. Zero spotting skill ≠ blind. It means you have
base ability to spot things, whatever that is. There's plenty of reasons why an ambush party can be hidden in a seemingly flat expanse.
Dogs don't actually see too good, and our taller stance gives us a larger range to see things. We have a better chance at spotting things than a dog, at least during the day. While dwarves are short, they stand taller than the average dog, so dwarves have a range advantage over dogs. Furthermore dwarves can see in the dark, so their advantages are preserved at night. Dogs would rely cheifly on other senses to detect intruders at distance, like smell and hearing. Dogs being bad at visual spotting is entirely appropriate.
http://en.wikipedia.org/wiki/Sighthound
Spotting skill: 0. Chance of seeing targets: 0. Sense: 0.
If detection was covered by senses, sighthounds could be bred. Also, senses covers more than just eyesight so dogs in general would be good at detection. Currently, as you have to admit, they are unable to be better than dwarves at seeing, smelling or hearing things.
Wow! Are you saying that DF skills/abilities framework needs improvement? Well, knock me down with a feather, but I'm shocked!
Could it be that supposedly intelligent creatures being so diligent in their work that they starve themselves to death or fall asleep in the halls even though they have a perfectly good bedroom available may need some improvement in the brains department?

Will you drop this "Zero skill = zero ability" strawman now? Zero skill means average ability, and for the case of dogs, it means average ability for a dog — whatever that may be. It needs some fiddling, but when has that not been the case in DF?
The important question about adding a skill in DF is not whether or not you learn by doing it in real life, but as to whether or not adding a skill makes the game more realistic than not having the skill.
Student as a skill is much less realistic than simply ignoring the experience factor, unless you had a great deal more complicated calculations to add to learning that you simply don't have at this point (student/teacher's interest in the subject, distractions in the classroom and on their minds, quality of materials to learn from/practice with for example.) And more than likely, it'd follow the same ludicrous exponential speed growth that the Legendary skill level currently has (which should be nerfed in pretty much every job, IMO) which is pretty bad. If the effects of the Student skill were capped to, say, a student with no experience learning at half the rate of a legendary, then I wouldn't mind as much (but it still would be worse than no skill at all.)
Quite frankly, I haven't seen very much effect of the student skill
at all, even when I have cranked it up to Legendary levels. While I take note of the caution, I think your concerns are a tad overblown.
If realistic, spotting as a skill should be continually exercised from birth. And the experience rewards for it should be lessened such that not everyone is a legendary spotter by 2.
This argument is based on the strawman that zero skill = zero ability. It doesn't. It means
average ability. I
certainly couldn't construct a bed that would be of any usable quality — you'd probably be more comfortable on the floor than in one of my beds, yet dwarves that have Not Carpenders on embark are able to punch out standard quality beds that work as well as any. Same story with trap mechanisms: a mechanic-in-name-only is able to make a mechanism that works reasonably well first try. If I tried that, it would be a worthless POS. The obvious conclusion is that a dwarf, upon reaching adulthood, is assumed to have some basic competence in many fields already, probably from what passes for dwarf school. Therefore, zero skill = average competence.