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. According to a former The Sims 4 developer, that lack of foresight is entirely by design—even though he spent years trying to change it. At Digital Tech Explorer, we love diving into the AI and logic behind our favorite gaming titles, and this revelation provides a fascinating look at the software engineering hurdles of life simulation.

David “Rez” Graham, who served as the lead AI programmer for the original release of The Sims 4 over a decade ago, recently shared insights into the challenges of creating autonomous digital lives. Currently the director of game programming at San Francisco’s Academy of Art University, Graham explained that while players might want their Sims to be smarter, giving them too much agency can actually break the game’s magic.

The “Hedonistic” AI Loop

“Sims don’t plan anything,” Graham explained. The game approximates human decision-making by having Sims constantly reassess their situation on a rapid cadence. At any given moment, a Sim asks themselves: “What is the next thing that I want based on my motives, traits, and environment?”

This explains why an autonomous Sim won’t decide to go to bed early specifically so they can wake up for a morning jog. Instead, they might stay up until 2:00 AM playing PC games because their “Fun” motive is low, completely ignoring the consequences of the next morning. While Graham notes this is “painfully realistic,” it is actually a result of the AI’s inability to look beyond the immediate present.

The Challenge of “Telegraphing” Intent

Graham revealed that developers on both The Sims 3 and The Sims 4 attempted to implement long-term planning systems, but these ideas were repeatedly—and “rightfully”—shot down. The primary hurdle was not the logic itself, but how to communicate that logic to the player.

“The problem with game AI is you have to telegraph it,” Graham said. He illustrated this with a real-world example: if you see someone go up an escalator and immediately turn around to go back down, you might assume they just realized they were on the wrong floor. However, in a video game, a player watching that same behavior would assume it’s a bug.

To bridge the gap between complex technology and player perception, the following table illustrates the difference between “Planned AI” and the current “Reactive AI” used in The Sims 4:

Avoiding the “Fish Tank” Effect

Beyond technical limitations, there is a fundamental gameplay reason for keeping Sims short-sighted. The Sims is built on player-driven storytelling. If the Sims became fully autonomous and capable of planning their own lives perfectly, the player’s role would be diminished.

“As soon as sims have too much autonomy, then what is the player doing except watching a fish tank?” Graham remarked. He noted that even as a “storyteller” type player himself—someone who often turns off aging to control every life stage—he recognizes that the game needs to leave the “big picture” decisions to the human behind the screen.

A Legacy of “Crazy Ideas”

Reflecting on his time at Maxis, Graham noted that many ambitious AI concepts were cut to maintain the game’s scope and focus. While he still believes there is a middle ground between “fish tank” autonomy and total dependence, he stands by the decision to keep Sims as the reactive, impulsive characters fans have come to love.

For now, if you want your Sim to have a productive morning, you’ll have to keep being the brains of the operation. Whether we are looking toward AI acceleration in future titles or staying with the current mechanics, the player remains the ultimate architect of the Sims’ world.