I once had a very boring task that was part of my research (to do with rayon chemistry not the brain). I have never done anything as boring before or since. I had to time how long it took for 100 drops to fall from a tiny hole. So I had to keep a count without losing my place and I had to see and register each drop. It usually took between 5 and 10 minutes for 100 drops to fall. The problem was that there was no rhythm. There might be 2 mins between a pair of drops or there could be 3 or 4 drops almost touching one another. This meant that my whole attention was taken up with watching and counting. I could not let my mind wander at all. After a run, I was worn out with fatigue and had to recover before I could face another run. I often failed in this simple (mindless) procedure and ended up not knowing where I was in the count or whether I had see the last drops. I was only using a tiny bit of my brain and forcing the rest to sit quietly and not even ‘drum its fingers’. An item in ScienceDaily reminded me of that long ago task. (here)

Levinson, Smallwood and Davidson looked at the relationship between working memory and attention. When the task does not use all of someone’s attention – how do they use their idle resources?

The researchers asked volunteers to perform one of two simple tasks, either pressing a button in response to the appearance of a certain letter on a screen, or simply tapping in time with one’s breath - and compared people’s propensity to drift off… People with higher working memory capacity reported more mind wandering during these simple tasks, though their performance on the test was not compromised…. What this study seems to suggest is that, when circumstances for the task aren’t very difficult, people who have additional working memory resources deploy them to think about things other than what they’re doing.

Interestingly, when people were given a comparably simple task but filled with sensory distractors, the link between working memory and mind wandering disappeared. Giving your full attention to your perceptual experience actually equalized people, as though it cut off mind wandering at the pass….In essence, working memory can help you stay focused, but if your mind starts to wander those resources get misdirected and you can lose track of your goal. Many people have had the experience of arriving at home with no recollection of the actual trip to get there, or of suddenly realizing that they’ve turned several pages in a book without comprehending any of the words. It’s almost like your attention was so absorbed in the mind wandering that there wasn’t any left over to remember your goal to read.

Where your mind wanders may be an indication of underlying priorities being held in your working memory, whether conscious or not. But it doesn’t mean that people with high working memory capacity are doomed to a straying mind. The bottom line is that working memory is a resource. If your priority is to keep attention on task, you can use working memory to do that, too. (But it can be very tiring, I remember.)