In short, here is the most important thing I've learned in chasing behavioral game design:
Almost all game activities are reducible into 3 base classes.
Those classes of actions can trigger neurochemical rewards.
The classes are:
- Amassing value - collecting food or abstract symbols of value, like gold or points
- Skills display - building and showing skills to potential mates and/or rivals
- Politics - participating in the unresolvable debate between hierarchy and equality
This is true because animals, like us, are motivated by the need to feed and breed.
Games predate humankind. We've all seen kittens or puppies play games that teach them adult skills - ludic games. As children, humans play dolls and war and house and cops & robbers for the same reasons.
We inherit this deeply rooted game wiring from our animal ancestors.
The primary differentiation between types of animals is diet - herbivore or carnivore. These survival strategies require changes in both GI tract and brain. Calves and lion cubs play different games to learn. Since we are omnivores, we can learn like an herbivore or like a carnivore.
Herbivores often live in bigger groups and have a more level social structure. Their business is life. They amass territory, food, mates and offspring.
Carnivores often live solo or in small packs or prides with a strict hierarchy. Their business is death. They rely on skills like speed, stealth and cunning.
Social creatures of any type need to coexist peacefully enough to protect or at least not harm their own offspring. The balancing of the struggle for dominance in a hierarchical system with the familial equality of food sharing is the main feedback loop influencing group peace and stability.
Sonic the hedgehog amasses gold coins and is skilled at running and jumping. He defeats the hierarchical Alpha and frees his woodland friends to promote a more equal system.
Football players amass territory. The herbivore-like defensive squad holds the grass plain, like Bulls. The predatory offensive team uses skills like running and passing to take land. There are on-field leaders but they still are one team. Potential mates, symbolized by cheerleaders, look on and signal approval for feats of skill. Potential rivals, on the opposing team also watch.
Our FPS games let you amass weapons, money and ammo. They certainly require you to level up your skills in view of other humans. The multiplayer interaction within the squad provides a rich political mechanic.
Early in design, ask yourself, what can players amass here? What skills will they learn as they go? Who will see them, who will oppose them socially? IF you do, you'll discover a natural feeling kind of gameplay that is easier to balance and more rewarding for players.