Have you ever interrupted someone with a quick question only to have them stare at you for a moment?
This is not always a stare of annoyance, or disapproval. If you look carefully, you can see the mental gears shifting, as they orient to the new situation.
Before someone can answer a question, or acknowledge you with some facial expression, they have to do some mental bookkeeping first.
When we’re interrupted, we have to clear working memory from the current task, and start it on the new one. In other words, we have to switch contexts.
In a digital computer, context switching follows a sequence similar to the following:
1. The current state of the process, including the content of the registers onboard the CPU, is saved to RAM.
2. Instructions and data for the new task are loaded into the registers.
3. Computation proceeds on the new task until it is completed, or interrupted.
4. If interrupted, the state of the process, including the content of the registers, is saved to RAM.
5. The state of the original task is retrieved from memory and loaded into the registers.
6. Computation proceeds on the original task.
This is a complex process, which involves work in its own right.
And it takes time.
In the brain, complexity runs on a whole other level.
When interrupted,
– we can’t just flush working memory and be done with the old task;
– it’s not clear what information we need in order to proceed with the new task.
Letting go of an old task is a physical process, like turning off a light. It takes time for the bulb to cool.
Locating what we need for the new task is a physical process too, one that involves a cascading activation of neurons.
Like water flowing through a branching streambed, the activation spreads across the brain into the recesses of the mind, to locate information pertinent to the new task, and bring it under the grasping focus of working memory.
It takes effort, and it takes time.
And that’s just the beginning.
