Sunday, August 17, 2025

"Researchers uncover surprising limit on human imagination"

From the Harvard Gazette, August 13:

Humans can track a handful of objects visually, but their imaginations can only handle one

Human beings can juggle up to 10 balls at once. But how many can they move through the air with their imaginations?

The answer, published last month in Nature Communications, astonished even the researchers pursuing the question. The cognitive psychologists found people could easily imagine the trajectory of a single ball after it disappeared. But the imagination couldn’t simultaneously keep tabs on two moving balls that fell from view.

“We set out to test the capacity limits of the imagination, and we found that it was one,” said co-author Tomer D. Ullman, associate professor in the Department of Psychology. “I found this surprising, so I can understand if others do, too.”

Ullman, who heads Harvard’s Computation, Cognition, and Development lab, has a long-time interest in what is known as intuitive physics. Think of the brain conjuring a ball as it rolls downhill, or sounding the alarm over two objects on a sure-fire collision course.

“How do we interact with the physical world around us?” wondered Ullman, who is also affiliated with the Kempner Institute for the Study of Natural and Artificial Intelligence. “I subscribe to the theory that the brain may be running mental simulations, kind of like a video game.”

These couldn’t be perfect simulations of physical environments, right down to the level of atoms and molecules. So Ullman’s lab has worked to understand what kinds of hacks and workarounds make mental simulations possible.

“The human imagination is just really cool, and we find a lot of people are quite interested in how it works,” he offered.

A sizable body of research has explored the capacity limits of human perception, or how many objects the brain can track in a visual scene. “Maybe you’re a parent watching multiple kids, or maybe you’re a lifeguard on duty,” Ullman said. “Obviously you can’t keep track of everything.”

Neuroscientists, psychologists, and computational modelers have found visual tracking is limited to just a handful of moving objects. But few have explored the imagination’s capacity limits....

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