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.
No sessions yet.
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.
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.
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.
Practice. Studies show 50%+ of dual-task cost can be reduced through training — but the cost never goes to zero.