Participants in that study read text on a computer screen while a sensor recorded their eye movements. From time to time the participants were interrupted and asked if their mind had just been wandering, or if they were concentrating on the text. Sure enough, the eyes blinked more while the mind wandered than while it focused on the task.
In another eye study, researchers at the University of Pittsburgh studied eye movements as participants read sections from a book. The psychologists initially had their subjects read the dense, often disturbing prose of Franz Kafka, but that required so much concentration that there was little evidence of wandering minds. So they switched to Jane Austen's "Sense and Sensibility."
The participants pushed a button when they felt themselves zoning out. During that time the eyes tended to fixate on words, as if they were just "mechanically plodding along," the researchers reported. But when they were concentrating on the text, the eyes zipped from word to word, showing that the participants were reading normally.
Incidentally, another Pittsburgh study found that readers really zone out if they are craving a cigarette.
And a third study from Pittsburgh found that even a moderate dose of alcohol increases mind wandering. But the drinker is unaware of it.
Finally, a Harvard University study concluded that "the mind is a frequent, but not happy, wanderer."
Psychologists Matthew Killingsworth and Daniel Gilbert collected 250,000 data points from an iPhone app on participant's thoughts as they went through their daily lives. The 2,250 participants were doing such things as walking, eating, shopping and watching television, and they reported that their minds were wandering 46.9 percent of the time.
"This study shows that our mental lives are pervaded, to a remarkable degree, by the non present," the study concludes. The researchers said the mind ignoring the present is a sign of unhappiness; thus a wandering mind is an unhappy mind.
However, there was one activity that the participants in the Harvard study said left them happy and sharply focused.
It was, they said, "making love."