EA Playfish’s The Sims Social “officially” launches today on Facebook, but it’s been playable in beta form long enough for people to have formed in-game relationships that challenge traditional social game interactions.

In The Sims Social, it’s possible for Facebook friends to become neighbors, which is standard for a multiplayer social game experience. Neighbors can visit one another to earn bonus energy and join friends in using whatever devices or activities the friend has purchased for their virtual home. Sims Social takes it one step further, however, with a social interaction system lifted from the original Sims franchise of games where dialogue trees guide individual Sims along a progression toward friendship, romance, or animosity, with each new “level” of relationship opening up new social interactions.

The most interesting feature of this relationship system on Facebook is the compulsive need for permission. Because gameplay is asynchronous, EA Playfish has introduced a system of invites that notifies players when their Sim has reached a new possible level of relationship with another Sim. This does not happen at all relationship levels (e.g. Introduction, New Friend, etc.), but rather at crucial levels of interaction where the relationship dynamic changes dramatically (e.g. Dating, Enemies). Once these invites are accepted, new interaction types are available for users to try — or can happen autonomously as a result of “free will” built into the game’s engine.

This presents players with interactions never before available in a social game. For example, we took our Sim to a neighbor’s house and initiated a Flirt. Because our neighbor was already in a Dating relationship with another Facebook friend, the game prompted us to ask that friend to break up with their partner. Though some romantic interactions were still available to us (e.g. Romantic Kiss, Give Flowers), the relationship could not progress until our Facebook friend ended his relationship with the other Sim.

This was the Facebook Message he sent in response to the Sims Social invite to leave their romantic partner for our Sim:

We spoke with Tom Mapham, a producer on The Sims Social, to better understand the gameplay systems at work and how this could impact a Facebook user’s social graph. In the traditional Sims games, there were no real obstacles to a player “cheating” on a romantic partner, save for the romantic partner developing jealousy that expressed itself in hostile actions (e.g. kicking over your Sim’s garbage can, slapping your Sim, etc.). Because the romantic partner in The Sims Social is controlled by an actual person, however, this jealousy mechanic doesn’t translate to a social game, and so Mapham says a gameplay choice was made to limit romantic partnerships to one per Sim.

“We felt that being able to date 30 other Sims at the same time would lose any connection to real relationships,” he says. “So at present Sims can only sustain one romantic relationship at a time. The game is a live service in beta and we will continue to review the design based on player feedback.”

At present, the game doesn’t use a player’s social graph beyond the friends list — so there’s no way for Sims Social to know that our friend indeed is engaged to another Sims Social player in real life. This gives the player, more or less, total control over how much of their real life they want to replicate or parody in the Sims Social. Though again, Mapham says, the team is open to player feedback on the matter.

As for sexual relationships (here called WooHoo), Mapham explains that Sims must reach a certain relationship level before it becomes a gameplay option, which involves a series of invites to progress to that level.

“Once that relationship level is achieved,” he says, “your Sim can ask another Sim to WooHoo and can even WooHoo autonomously. It does not need another ‘handshake’ from your friend.”

The Sims Social officially launched today on Facebook. According to our traffic tracking service, AppData, the game currently has 4,859,046 monthly active users and 2,064,153 daily active users.