The more I think about MMOG design, the more importance I place on recognizing that people have different playstyles. What's "fun" for one person is boring to another. So games need to be designed with this in mind; designers ought to understand the major playstyles and evaluate every game mechanic according to how it supports the preferred playstyles of their intended audience.
Assuming we can agree that there are such things as "Achievers" and "Explorers," and that both kinds of gamer are worth attracting, how can we uniquely reward each of these playstyles? (Note: I believe Socializers are also worth attracting, but that's a different thread.)
To appeal to each of these types I come back to the main difference between them, which I believe is an emphasis on what is concrete versus what is abstract.
Consider the old adage "give a man a fish and he'll eat for a day; teach a man to fish and he'll feed himself for a lifetime." You can imagine this kind of conversation between an Achiever and an Explorer in a MMOG. The Achiever walks up to an Explorer and asks, "Hey, is the fishing good here?"
The Explorer, assuming that the Achiever needs a long-term solution, will reply by explaining how sunlight, air temperature, water convection rates, and local vegetation patterns interact to determine how likely the fish are to be biting in any place at any time of day.
After about ten seconds of this, the Achiever reaches into his backpack, pulls out a Potion of Exploding, throws it into the water, and walks off with an armful of the fish that float to the surface. And the Explorer will be left standing there with his jaw hanging open.
What's going on here is that we have different concepts of what's important, but we tend to assume that everyone else shares our style. When that proves not to be true, we're surprised; we assume that the other person is a fool or a nut. In fact, they're just operating under a different set of rules about what really matters than the rules that we use.
In the case of Achievers and Explorers, what really matters starts with externals and internals, with form and function, with concrete facts and abstract theories. (It doesn't end there, but it's the most important difference.)
For the Achiever, things and data are more valuable than ideas and feelings. Intangibles like perceptions and theories and concepts aren't "real"; they aren't things that can be collected and stored and spent and measured. So Achievers prefer rewards that are immediate and material. The bigger the pile of stuff, the more security you have in an inconstant world. (Killers, whom I prefer to think of as "Manipulators," also prefer concrete rewards. But because their secondary motivation is change rather than the Achiever's desire for stability, they're much more interested in spending than in saving. Manipulators lust for the thrill of the kill, the rush of the object- or person-manipulating experience.)
Explorers don't see as much value in objects as Achievers. As far as the typical Explorer is concerned, anyone can collect tokens; what really matters is the knowledge of the principles and effects of token-collecting. Explorers value seeing beyond the external forms of things into the internal rules that determine the functionality of things. Knowledge about a thing isn't particularly worthwhile unless it gives you some insight into the structure of that thing and the nature of that class of things.
So what about MMOGs? What does all this analysis tell us about specific game systems and mechanics for rewarding both these kinds of gamers?
As noted earlier, the Achiever's preference for concrete rewards makes them relatively easy to satisfy. Cash and shiny loot, accurately keyed to the difficulty of the challenge that was overcome to obtain them, are the main motivators for Achievers. After that come the more social rewards, which we can summarize as "badges" -- that is, public indicators of achievement. If you offer them the chance to collect money, an interesting variety of pretty loot, and plenty of public status markers, Achievers will play. (Note that these three rewards constitute short-term, medium-term, and long-term inducements to continued play.)
Explorers are harder to satisfy because their needs are more abstract. The key may be to consider the difference between surface data that can be collected in bulk by immediate observation (which Achievers can do) and analysis of data within which patterns can be discerned and from which principles can be derived (these being Explorer specialties).
This why I keep harping on depth of systems. If all you have are surface connections, Achievers will quickly do whatever grinding is necessary to list those. Game over, man! But if there are deep and nonlinear connections within and between systems -- if different configurations produce different effects, and if those connections can't be fully understood by simply grinding through all the possible options -- then the people most likely to master these systems are Explorers.
To summarize: Achievers can discover facts, but Explorers discover principles. Explorers will love a game that has deep principles and rewards the discovery of those principles by the truly curious player. In a word, let Explorers "tinker" with things. We love that; we'll spend all day tinkering with things if you let us, and we'll feel rewarded in the process of tinkering.
Another way of highlighting this difference between Achievers and Explorers can be summed up in the words "factory" and "laboratory." Where an Achiever will usually be interested in Production and Sales, an Explorer is more likely to gravitate toward Research and Development.
Explorers want to be "creative." The opportunity to create new things will draw Explorers like honey draws bears. But note that "create new things" does not mean "crank out a bunch of identical new objects." That's Production, and it bores Explorers. (On the other hand, designing a new process that increases productivity might not be boring at all to some Explorers.)
What Explorers want most, I believe, is the opportunity to design uniquely new objects. A game that requires creativity and a deep understanding of functionality to develop an entirely new class of objects, and which permits players to do so, would instantly capture the enthusiasm of every Explorer. Even better would be if this included the possibility of designing very large and extremely complex systems that allow other players to tinker -- you wouldn't be able to keep most Explorers away from such a thing! (Explorers aren't tool-users; they're tool-builders.)
Unfortunately, this is tough to offer in a multiplayer game. "Sandbox" virtual worlds allow players to create new objects. Second Life, for example, lets players use its scripting system to create interesting new objects which can then be manufactured for other SL players. Explorers tend to love Second Life for this reason. But virtual worlds such as WoW and SWG that are much more game-like almost never allow this level of creativity from players. In the first place, there are technical constraints to allowing anyone/everyone to generate unique kinds of objects; in the second place, there are serious gameplay balance concerns related to giving players design powers; and in the third place, publishers cite potential legal questions of who owns the "new" player-created objects.
Having said all this, I believe there's an opportunity for a clever developer to allow some kind of R&D feature in a game world. Personally, I'd love to see this in a MMOG in either a system allowing the design of new objects or new magic spells (or, best of all, a way for intrepid players to discover new ways to combine these two disciplines). But I recognize the difficulty in this; it may simply be too time-consuming to create such a powerful feature when there are more critical gameplay features that must be developed. (Although I would argue that offering such an Explorer-friendly feature would go a very long way toward creating a valuable balance between Achiever and Explorer subscription numbers.)
Finally, it's possible that, rather than an in-game reward, Explorers might be better motivated by meta-rewards, by benefits provided not in the game but outside the game. (Presumably Achievers would find such rewards less satisfying.)
Membership in something like an "Inventor's Network" or "Arcane Association" might be a nice reward for players who demonstrate both a strong understanding of the principles of the more abstract gameplay features and a willingness to help other players understand those features. (The alternative of letting anyone mark themselves as a "Helper" was tried in SWG. Mostly it just resulted in anyone so marked getting pestered for handouts by beggars.)
I suspect it's the more social Explorers who'd value membership in a group as a reward, though. Extroverted Explorers would probably enjoy such organizations. The less social Explorers would probably prefer rewards that recognize curiosity and creativity without requiring interaction with strangers.
Honestly, "how to reward Explorers" is a really hard problem. We don't even know how to do this properly in real life! The typical Rational (Explorer) who quietly figures out a principle will inevitably be overlooked by the company they work for, while the Guardian (Achiever) or Artisan (Manipulator) who applies the principle reaps the credit, the cash, and the promotion. Application is just easier to see and appreciate than design -- it's simply how we humans work, and I don't seriously expect the developers of a multiplayer game to figure out a solution to that when so few others have.
The best I can suggest is this: be aware that there are Explorers, and that they have useful roles to play in a persistent game world. Try to design game systems for them to explore in creative ways, but don't offer concrete rewards for doing so -- focus instead on building world systems so deep and technically rich that discovering their secrets is a satisfying long-term process in and of itself.
That should work. :)