'Feature interference,' and why your brain struggles with uncertain tasks
Multitasking feels like a required skill in modern life, but as anyone who has tried to keep track of multiple chat windows, an email inbox and a stream of phone notifications during a video call can tell you, figuring out which messages are important comes at a cost.
In modern life, multitasking is often seen as a necessary skill, but performing multiple tasks simultaneously can be challenging for the brain. A new study by neuroscientists at the University of Chicago, published in Nature Neuroscience, reveals that limits to our ability to juggle multiple tasks arise from interference between the brain's representation of different inputs, particularly when their relevance to a given task is uncertain.
The brain can handle many different things, but keeping them distinct becomes difficult when the brain is under high cognitive load. Marlene Cohen, a professor of neurobiology at UChicago and senior author of the study, explains that when information gets mixed together in the brain, even if it is well-known, it leads to difficulties in task performance.
To understand why multitasking is so difficult, researchers led by postdoctoral fellow Cheng Xue conducted experiments with over 200 human participants. Participants watched a series of images on a monitor, each consisting of a striped circle that rotated or changed size. They were asked to track a specific feature of the circle and report the change they observed.
Sometimes, they were never told which feature they should track, introducing uncertainty. Under these conditions, participants performed poorly, indicating that the brain was struggling to filter out irrelevant information.
The researchers found that when people were uncertain about which feature to focus on, their brains held onto irrelevant visual details, contaminating their decisions and making it harder to perceive what mattered most. Similar results were observed in two trained rhesus monkeys, who also experienced feature interference when making choices under uncertainty.
By examining the neural activity of the animals, the researchers discovered that separate groups of neurons encoded visual features, but when uncertain, these visual representations became mixed up in the same sets of neurons—a phenomenon they call feature interference.
This research suggests that multitasking struggles are not due to a lack of willpower or discipline, but rather a hardware limitation in the brain. The findings may provide insights into cognitive diseases, such as Alzheimer's, and help improve diagnosis and treatment. To improve multitasking, the researchers recommend focusing on one task at a time, allowing the brain enough time to switch gears.
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