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Brain exercise

The Hidden Cost of Changing What You Are Doing

Two rules that keep swapping. Each is trivially easy. Alternating between them is not.

Blue panel: odd or even. Orange panel: bigger or smaller than five. Eighteen trials.

This is a demonstration of an effect, not the clinical task it resembles. It uses different stimuli, has no normed scoring and no cut-offs, and no result here is interpreted. Clinical versions of tasks like this are administered under controlled conditions for good reasons.

What just happened

What people call multitasking

  • The last rule was still loadedThe rule you just used does not vanish when the panel changes color. It lingers and has to be actively replaced.
  • The trial after a switch is the slow oneThis is the switch cost. It appears in nearly everyone and is remarkably consistent within a person.
  • Neither rule was hardThat is the point. The difficulty is not in either task. It is entirely in the changing between them.
Diagram from Chicago Brain Health showing a run of trials under two rules, with the extra time landing on the trial immediately after each change of rule.
The cost lands on the trial after the change

With few exceptions, people do not do two demanding things at once. They alternate rapidly, and pay a switch cost every time.

The costs are small individually and add up substantially across a working day full of interruptions. That is a large part of why a fragmented day feels so much more tiring than a focused one with the same amount of work in it.

A quick note. Feeling clumsy right after the color changes is the expected result and is what the activity is built to produce.

Square illustration from Chicago Brain Health of two columns of colored blocks representing two rules, with orange links marking every point where the rule changes.
Every orange link is a switch, and every switch costs

Science vs hype

What this does not mean

What you may have seen. Switching tasks presented as executive function tests, multitasking scores, or as assessments of cognitive flexibility you can self-administer.

What this activity actually involves. A task-switching demonstration using digits and two simple rules. It reports a count and elapsed time and nothing else.

Where the evidence stops. Switch costs are real and reliable in controlled settings. This version has no norms, no controlled timing and no interpretation, so it cannot tell you anything about your executive function or any condition, and it is not a screening tool.

A desk at the end of the day covered in several half-finished things at once
Several half-finished things at once

Who Can Use This One

  • Vision is required, including telling the blue and orange panels apart. The rule is also stated in the instruction line for anyone for whom that distinction is unreliable.
  • No time limit per trial.
  • Keyboard operable, every choice is a real button.
  • Nothing is recorded. No account, no score stored, nothing sent anywhere.

The Day That Leaves You Exhausted With Nothing Finished

You just paid a switch cost eighteen times in about a minute and could feel it happening. Most people pay it hundreds of times a day without ever noticing.

That is often what is underneath “I cannot concentrate any more”. Sometimes the answer is the environment. Sometimes it is sleep, or mood, or thyroid function, or something that has been there since childhood and was never named. Those look identical from the inside and quite different on assessment.

That conversation is free, and we will tell you plainly when the answer is that you do not need us.

If you would rather read first, our conditions page sets out what neurofeedback is used for and how strong the evidence is for each, and our research page covers what the studies actually found, including the ones that came out negative.

Let’s chat

A free conversation with a psychologist. No intake form, no obligation, and we will tell you plainly when the answer is that you do not need us.

These activities are demonstrations of how perception, attention, memory and movement work. They are not tests, screenings or diagnostic tools, and no result here says anything about whether you have a medical or psychological condition. Nothing on this page is medical advice or a substitute for evaluation by a qualified professional. Last reviewed September 2026.