A study says multitasking has a hidden problem: How does your brain decide what matters?

Your phone lights up halfway through a meeting. A colleague wants a quick answer. You start typing while someone explains a deadline. A moment later, you look up. You heard the speaker, yet you cannot explain what they said.

Perhaps you blame a short attention span. Researchers at the University of Chicago offer another explanation. Trouble can arise when the brain struggles to separate useful information from distracting details. The question is not only how much you are doing. Knowing which information matters can also shape how well you do it.

Why multitasking can confuse your brain

In a study published in Nature Neuroscience, researcher Cheng Xue and colleagues explored what happens when people are unsure which information should guide a decision.

More than 200 participants viewed striped circles. Between images, the stripes could change direction or size. Participants had to judge the relevant change.

Sounds straightforward. One complication made the task harder. Nobody told participants which feature mattered. They worked it out from feedback. The relevant feature also changed periodically.

Imagine answering a math question without knowing whether the teacher wants you to compare numbers or add them. You can see the numbers perfectly. Choosing what to do with them is the problem.

Participants made less accurate choices when the task was uncertain. Their performance improved as they worked out the rule.

What “feature interference” means for attention

The researchers called a key mechanism “feature interference”. Information that should have stayed separate became harder to keep apart.

During uncertain tasks, irrelevant features had stronger representations. Different features also became more tangled in patterns of neural activity.

Think of two conversations reaching you at once. Both contain words you understand. Following the right conversation becomes harder when you cannot keep them separate.

Senior author Marlene Cohen explained that the difficulty was not losing information. The brain could retain it while struggling to separate the features needed for a decision.


The team combined human experiments with computer models. They also recorded brain activity in two rhesus monkeys completing similar tasks. The neuron recordings came from monkeys, not the human volunteers.

The findings suggest that interference helps explain some performance problems under uncertainty. They do not establish that every multitasking mistake has the same cause.

Cognitive control: how your brain keeps a goal in view

Return to the meeting. Your goal was to understand the deadline. The message introduces a competing goal: answer your colleague.

Neuroscientists Earl Miller and Jonathan Cohen proposed a theory of cognitive control. Their account describes how the prefrontal cortex maintains goals and guides processing elsewhere in the brain.

In everyday language, a clear goal helps your brain give useful information priority. Reading a worksheet offers a simple example. If you need to find the largest number, number size matters. If you need to identify odd numbers, a different rule matters.

The information stays the same. Your goal changes what deserves attention. Miller and Cohen’s theory provides helpful background for understanding relevance. It is a separate account, rather than a conclusion newly established by the Chicago experiment.

Task switching explains the struggle to get back on track

Another familiar problem appears after you send the reply. Returning to the meeting takes effort.

Psychologist Stephen Monsell reviewed research on “task switching”. People generally respond more slowly and make more errors immediately after changing tasks.

Researchers call the difference a “switch cost”. Your brain needs to adjust its “task set”, meaning the rules and mental operations needed for the current activity.

Typing a reply requires one task set. Following an explanation requires another. Preparing for a switch can reduce the cost, although it usually does not remove it completely.

Switching costs help explain why a brief interruption can feel longer than the notification itself. The Chicago study adds a related concern: uncertainty can make relevant and irrelevant information harder to separate.

How to make competing tasks easier to handle

Before answering the next message, decide which task needs your attention now. If the deadline explanation matters, finish listening. If the reply is urgent, pause deliberately and return afterwards.

Xue suggested doing one task and letting time transition. The experiment didn’t directly test whether silent notifications improve meetings. Such changes are practical applications to consider, rather than proven results from this study.

FAQs

Does multitasking always fail?

The study found poorer performance when the relevant task was uncertain, so it can fail but it can also succeed.

Is uncertainty the same as distraction?

No.” Uncertainty means being unsure which information or rule should guide your decision.