'Sims don't plan anything' says former Sims 4 developer, though he always wanted to program them to: 'it's always shot down, rightfully so'

At their core, sims are hedonistic little squirrels constantly meeting their needs one moment at a time without any ability to think through a sequence of actions. That's by design, one Sims 4 developer says, but he always wanted sims to have a more thoughtful approach to their own lives when left to their own devices.

David "Rez" Graham is now the director of game programming at San Francisco's Academy of Art University and the developer on his own unannounced game, but served as lead AI programmer for the original release of The Sims 4 over a decade ago. In an interview with PC Gamer, Graham shared the challenges inherent in making more autonomous sims.

"Sims don't plan anything," Graham explained. The Sims approximates how humans make decisions, but at any moment, they're constantly reassessing what they should do one objective at a time. "They run AI on a cadence and say 'what is the next thing that I want based on my motives, traits, whatever?'"

A player can fill up a sim's action queue with a series of tasks in a sensible order, but a sim can't autonomously decide to go to bed early so they have time to exercise before work in the morning like a person would, for instance. They stay up playing video games until 2 am which, yeah, painfully realistic, but not quite intentionally so.

"I've always wanted to have some level of planning in The Sims," Graham said. The lead AI programmer on The Sims 3 attempted it, he said, after which Graham himself attempted it on The Sims 4.

"It's always shot down, rightfully so, because the problem with game AI is you have to telegraph it," Graham said. He described watching someone ride up an escalator in front of him just minutes before and, after reaching the third floor, immediately turning around and riding the escalator back down.

"If we were in a game, somebody would laugh about that and say that's a bug or that that guy's entire job is to go up and down the escalators forever to show the illusion of life in a city. In reality, that guy was probably just like 'oh, I'm not supposed to be on the third floor.'"

A player watching that happen, Graham said, would need to see the character have some kind of reaction like a dialogue bubble or a spoken line to say "Oops, I'm on the wrong floor!" for them to believe that something intentional had happened.

Finding a way to telegraph the "thought process" behind a sequential set of actions a sim might take does sound like a pretty monumental task. If a sim could plan for that early morning workout, how would you show a player that going to sleep before the sim was tired was done with intent, and was not a bug?

More than that though, too much autonomous planning by a sim, even if done perfectly, may remove the fun for players, Graham said. "A big part of The Sims is players telling stories. As soon as sims have too much autonomy, then what is the player doing except watching a fish tank?"

Graham said that he considers himself a "storyteller" type player in The Sims, turning off aging and living out each life stage until he's ready to move on, so he can relate to not wanting to have the game wrest too much control away from him.

He believes there probably is a middle ground between fish tank-ifying the simulation and sims having no ability to plan ahead whatsoever, but he can see why the idea hasn't ever stuck.

"So many ideas that we had on The Sims got shut down," Graham said later on, talking about the balance needed to maintain scope and ship a game in a studio the size of Maxis compared with his current indie project. "Correctly shut down because they were crazy ideas!"