LAUSR

Dual-tasking is the ability to perform two tasks simultaneously. Dual-tasking measures a component of executive function as participants are required to coordinate their attention to both tasks while they are being performed. Dualtasking is differentiated from serial multitasking paradigms where individuals focus on and perform one task at a time, switching between those tasks. However, concurrent multitasking can be used synonymously with dual-tasking as the tasks are performed in parallel (e.g., talking on the phone while stirring a pan on the stove). In dual-tasking, the difference between performance on each of the tasks performed individually and simultaneously provides an index of dual-tasking cost. To accurately assess dual-tasking, the chosen tasks should not tap the same input modalities or response mechanisms (e.g., manual versus oral responses). Additionally, the two tasks should involve different cognitive contents (e.g., visual tracking with a word or digit task) to ensure the tasks do not interfere with one another. The tasks administered during dual task assessment may include digit, word or pattern recall, various monitoring tasks (e.g., box crossing or E-checking), tracking a target or continuous choice reaction-time tasks. Real life behaviours such as walking and talking have also been used. To provide a dual-task measure of the ability to coordinate attention between the two tasks, single-task performance is often titrated or calibrated for each participant's own single-task ability. This can be done by assessing and administering the tasks at an individual's own span or single-task ability levels or statistically controlling for single-task performance. Dual-tasking can be measured in terms of accuracy or response times with dual-task costs reflecting less accurate or slower performance when the two tasks are performed together compared to individually. Some studies consider dual task costs on the primary but not the secondary task while other studies consider any trade-off between the two tasks and assess overall dual task costs. Dual-task impairments are reported in Alzheimer's disease, where performance declines with disease progression, but deficits have also been found in Parkinson's disease, vascular dementia and traumatic brain injury. However, dual-task impairments are not found in depression and less consistently in mild cognitive impairment and healthy aging, especially when the tasks are titrated for individual ability levels.