Scientists Reveal the Human Imagination's Limit in Tracking Multiple Invisible Objects

Researchers have discovered a fundamental constraint on our capacity to imagine and mentally track multiple moving objects. In a recent study published in Nature Communications, cognitive psychologists tested how well people could visualize the trajectory of objects that disappear from view. Human participants were able to accurately predict the impact point of a single bouncing ball after it vanished, but their performance sharply declined when trying to track two balls moving simultaneously. This indicates that the human imagination is limited to effectively handling only one or two objects at a time when they are no longer visible.

Tomer D. Ullman, an associate professor at Harvard and head of the Computation, Cognition, and Development lab, explained that their initial hypothesis was that the brain could track about three or four objects in mental simulations. Interestingly, their experiments revealed that the mind predominantly employs a serial approach when imagining objects that have disappeared, moving from one object to another rather than tracking multiple in parallel. This insight sheds light on the underlying mechanisms of "intuitive physics"—the brain's ability to simulate real-world physical processes.

The study involved online participants viewing animations of bouncing balls, which then vanished, and recording their predictions about the objects' trajectories. Two computational models—parallel and serial processing—were devised to further understand mental tracking. Results showed that people performed well when tracking a single object or objects moving in tandem, but struggled with multiple objects, highlighting a fundamental limit.

These findings have broader implications for understanding how humans perceive and mentally visualize the world, from everyday tasks like watching children to professional activities like lifeguarding. Ullman emphasizes that understanding these cognitive limits opens exciting avenues for future research, particularly how the brain employs tricks and shortcuts in mental simulations.

This discovery advances our understanding of the capacity and limitations of the human imagination, especially in the context of visual and cognitive tracking, and may influence future studies in cognitive science and artificial intelligence.