This shows the bar charts of normalized response times. (a) for the math task and (b) for deviation task across 15 subjects. The filled black bar: case 1; dark gray bar: case 2; light gray bar: case 3; the open bar: single case. The response time for math task in dual-task cases (case 1, case 2, and case 3) is significantly longer than that for in single task (case 4). The shortest response time for the math onset is in case 4. The response time for deviation task in case 1 is significantly shorter than those in other cases. The longest response time to the deviation onset is in case 5. The bottom insets show the onset sequences of the two tasks.