I recently was on a long solo hike and my smartphone ran out of batteries. With no music or anyone to talk to I had to find something to think about for the 2 hours it would take to complete the hike. I ended up going through each year of my life and thinking about where I lived and what I was doing at the time and memories associated with each time and place. It was actually quite entertaining.
I go through this process while running. I highly recommend everyone to jog/run for about 30-40 minutes every day, alone, wit no music. It performs a "defrag" of your brain and relieves most of the stress and worries.
Sorry but I think you missed something. You should have let the emptiness and the boredom fill your self instead of proactively and orderly going through the years of your life.
a mindful / "zen" meditation would ask you to return to the state of being (i.e. not thinking) after you've noticed that you're thinking, but that's not the technique the scientists are suggesting in the OP, nor what the parent comment is talking about.
Searching for a topic to think about is the kind of creative process they're trying to encourage, and indeed it's not unlike a brief bit of mindfulness, in this case followed by a lengthy period of introspection. Assuming that the introspection doesn't fall into a negative spiral of memories and emotions, this is reasonably mindful in itself.
