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Multi-tasking

Multi-Task Reaction Cost

Two simple choice tasks. First, do each one alone (single-task baseline). Then do them at the same time. The cost in accuracy and reaction time is the dual-task interference score.

What makes this one different

Multi-task cost is a strong predictor of real-world driving safety and work performance. Most demos just say "try harder" — we compute the actual cost per block, so you can see whether practice reduces it.

Block Single → Dual
Trial 0
Task A: Color
—
Press F red · D blue
Task B: Letter
—
Press J vowel · K consonant
Ad slot.

Single vs. dual-task

History

No sessions yet.

What problem does it solve?

Dual-task interference is one of the most-replicated phenomena in cognitive psychology: doing two things at once is slower and less accurate than doing either alone. The "dual-task cost" is a measurable quantity — and a meaningful one. It's used in driving research, air-traffic-control studies, and ADHD research.

Who is this for

How to interpret your results

Dual-task cost of 50–150 ms is typical. Above 250 ms means heavy interference. Below 50 ms suggests you've automated one of the tasks well.

Limitations

  • Tasks are simple (color, vowel). Real-world multi-tasking involves overlapping stimulus-response mappings, which is harder.
  • Practice reduces cost. Run several sessions to see your learning curve.

FAQ

Can you truly multitask?

Most cognitive tasks can't be done truly simultaneously — your brain rapidly switches. The cost shows up as slower responses and more errors. Some highly practiced skill combinations (typing while talking) feel simultaneous but still have measurable cost.

How can I reduce cost?

Practice. Studies show 50%+ of dual-task cost can be reduced through training — but the cost never goes to zero.

How do I use Multi-Task Reaction Cost step by step without mistakes?Follow the order given in the usage section: Two simultaneous choice tasks. Compare dual-task cost to single-task baseline, plotted per block. The step-by-step part matters less than the unit check that sits inside it. Confirm every unit matches the thing you are actually trying to measure before you press calculate - that single check catches more wrong answers than any other habit, and it costs about ten seconds.
What are the common mistakes when using Multi-Task Reaction Cost?Most common mistakes come down to four habits: entering 20 when the field expects 0.2 because the field is a percentage; leaving a field blank and accepting the default without checking what it stands for; changing one input and reading a result that was calculated before the change; and quoting the output as an exact figure when the page describes it as a reference estimate. Press calculate again after any edit, and treat the number as a reference point rather than a final answer.
How do I read the result from Multi-Task Reaction Cost?Read the final figure first, then come back to this section for the conditions behind it: Dual-task cost of 50–150 ms is typical. Above 250 ms means heavy interference. Below 50 ms suggests you've automated one of the tasks well. Keep two things apart: the number itself, which comes from the values you typed, and the assumptions it depends on, which decide whether that number is meaningful. The page sets out what a higher or lower result means for your case, so check that direction as well as the magnitude.
Can I act on the Multi-Task Reaction Cost result directly?Treat it as one reference sheet before you decide, rather than as the answer itself: Tasks are simple (color, vowel). Real-world multi-tasking involves overlapping stimulus-response mappings, which is harder. Practice reduces cost. Run several sessions to see your learning curve. The output describes a magnitude under the conditions you entered. It does not include what it actually costs to act, what might change while you act, or how the other side behaves. Before you commit, compare the result against reality and note which assumptions do not hold where you are.
What inputs does Multi-Task Reaction Cost need?The inputs for this tool sit in the form area of the page - fill them in one at a time as prompted. Before you start, check that each one uses the unit you actually measured: mismatched units are the most common source of a wrong answer here.