5a. The Costs of Multitasking

Multitasking is essential in a multi-dimensional world with many competing priorities and demands.

However, the costs it places on our productivity, lifestyle and mastery are huge (bordering on catastrophic) and largely invisible to us.

This post outlines some of those not-so-obvious costs. The next post will offer some ways to contain and minimise them.

The Top 5 Costs of Multitasking

The primary costs of multitasking are in the prefrontal cortex. Its main responsibility is executive function: understanding, deciding between, memorising, recalling and preventing us from being distracted from complex things.

1. The Task-Interleaving Effect delays all interleaved tasks: the more tasks we interleave, the longer each task takes.  Interleave 2 tasks and each takes twice as long; interleave 3 and each takes three times as long.

How many tasks are you interleaving unnecessarily?

2. The Task-Switching Overhead is the extra mental setup time and energy needed when we return to a challenging task that we’ve switched away from.

Remember the 15 minutes from the previous post?  We incur it every time we switch back to an incomplete challenging task.

3. The Parallel-Processing Overhead is the extra task-management capacity our prefrontal cortex needs to manage multiple challenging tasks at the same time.

We need less than 10% of our total prefrontal cortex capacity to manage a single challenging task, but over 70% if we’re doing two challenging tasks at the same time.

Attempting three challenging things at once, requires nearly all of our prefrontal-cortex capacity, leaving very little for the tasks themselves. The lights may be on, but there’s no one (that intelligent) at home!

4. Neurochemical Depletion results from the brain-fuel-burning demands of  task-switching and parallel-processing.

The prefrontal-cortex – as the most newly evolved (i.e. primitive and inefficient) part of the brain – needs a very rich mixture of neurochemicals to operate effectively, so its performance is severely compromised by a lean mixture.

Worse, when the mixtures gets too lean, the prefrontal cortex becomes partially disabled and by-passed and more control is handed over to the the limbic “lizard brain” cortex, instead.  The result? Reduced executive function and performance and the absence of the thin veneer of hard-earned civilised sophistication that makes us easy to live with.

In a sense, we regress to caveman-style thinking.

Neurochemicals need at least a 24-hour cycle of nutrition, hydration, exercise, relaxation and deep sleep to be replenished, so the impact is long-lasting and cumulative over the work-week.

5. Arrested Mastery Development is by far the most concerning long-term cost of multitasking.

While the neural network development effect enables our brains to develop capability as we practice new skills, long-term mastery is accelerated by (and, in a sense dependent on) the myelination effect.

Myelination is the wrapping of biological electrical insulation (myelin) around the axons of the brain.  It seems to only happen during deep concentration and takes a while to get going and reach its maximum rate (12 to 16 minutes). It typically slows down after 40 to 60 minutes.

If we switch away from deep focus on challenging tasks inside of that time, we deny ourselves the benefits of myelination: mastery opportunity lost.

The effect of myelination?  Some neuroscientists estimate more than an IQ point a month!

Have I got your attention?

I hope that I’ve convinced you to think very carefully about reducing unnecessary multitasking: for the sake of your immediate and long-term health, intelligence, performance and lifestyle.

The next post will offer some ways of reducing multitasking and its effects – without having to give up the essential benefits of keeping up with our challenging world.