How does multitasking affect the brain and human performance?

Performing more than one task at a time is a desired ability, but is not an innate function for most of us. The human brain performs a single task by utilizing and integrating the functions of several brain regions simultaneously. In the process of catching a ball, our visual system tracks the trajectory, the pre-motor cortex anticipates the final descent and transmits specific signals to the motor regions to precisely place the hands where the ball is anticipated to land. Once the ball touches the hands, the sensory system triggers the motor system to clasp the fingers down on the ball.

Completing two tasks with parallel networks coordinating a completely separate set of precise neural integration activity does not occur naturally in the human brain. However, it appears that training to perform two tasks simultaneously can alter the brains chemistry to allow us to “learn” to perform multitasking abilities. The brain circuits involved in the first task appear to reorganize and “groups” a sequence of neural steps as one single step.1 This simplifies the brains processing of one task and subsequently “frees up” the brain to plan the execution of a second task without interference from the first.2

In the untrained brain, the performance of one task interferes with the brain activity required for a second task.3 Repeated practice with gradually introduction of a second task has been shown to reduce the interference of the first activity.4 Multitask “training” activates areas in the frontal section of the brain that inhibits signals that interfere with the execution of a second task. With repetition, the separate “brain networks” convert from a slow, deliberate processing rate to a faster automatic sequence of rapid communications between the involved brain regions. This phenomenon has been documented on functional MRI scans that identify neural activity levels in the various region of the brain. The comparisons clearly show a difference in areas of the brain involved before and after learning to multi-task.2

Additional research has revealed that multitasking is mastered as the brain requires less reliance the neural circuits involved in attention and concentration. These attention and concentration circuits are essential as we learn to perform an unfamiliar task, but new circuits form as the tasks are performed repetitively. This results in the formation of task-specific networks that are more efficient, require less attention and concentration, and ultimately become automatic.5

The effects of multitask training speeds up the sequence processing of a given task and prevent interfering of the second task. This essentially prevents neural “traffic jams”, or bottlenecks, where two sets of brain signals cannot be processed at the same time.

All of this science seems to correspond what our coaches and music teachers have always tried to teach us. Excessive practice does improve our performance and ability to perform two complicated tasks simultaneously.

1. Erickson KI, Colcombe SJ, Wadhwa R, et al. Training-induced plasticity in older adults: effects of training on hemispheric asymmetry. Neurobiol Aging. Feb 2007;28(2):272-283.

2. Erickson KI, Colcombe SJ, Wadhwa R, et al. Training-induced functional activation changes in dual-task processing: an FMRI study. Cereb Cortex. Jan 2007;17(1):192-204.

3. Ruthruff E, Pashler HE, Hazeltine E. Dual-task interference with equal task emphasis: graded capacity sharing or central postponement? Percept Psychophys. Jul 2003;65(5):801-816.

4. Ruthruff E, Johnston JC, Van Selst M, Whitsell S, Remington R. Vanishing dual-task interference after practice: has the bottleneck been eliminated or is it merely latent? J Exp Psychol Hum Percept Perform. Apr 2003;29(2):280-289.

5. Chein JM, Schneider W. Neuroimaging studies of practice-related change: fMRI and meta-analytic evidence of a domain-general control network for learning. Brain Res Cogn Brain Res. Dec 2005;25(3):607-623.