Blinking eyes might be a sign of a wandering mind, according to a new study in Psychological Science. Researchers from the University of Waterloo found that when subjects' minds wandered, they blinked more, setting up a tiny physical barrier between themselves and the outside world.

The study was inspired by brain research that shows, when the mind wanders, the parts of the brain that process external goings-on are less active.

Fifteen volunteers read a passage from a book on a computer. While they read, a sensor tracked their eye movements, including blinks and what word they were looking at. At random intervals, the computer beeped and the subjects reported whether they'd been paying attention to what they were reading or whether their minds were wandering — which included thinking about earlier parts of the text.

The participants blinked more when their minds were wandering than when they were on task. "What we suggest is that when you start to mind-wander, you start to gate the information even at the sensory endings — you basically close your eyelid so there's less information coming into the brain," says Cognitive neuroscientist Daniel Smilek, of the University of Waterloo.

This is part of a shift in how scientists are thinking about the mind, he says. Psychologists are realizing that "you can't think about these mental processes, like attention, separately from the fact that the individual's brain is in a body, and the body's acting in the world." The mind doesn't ignore the world all by itself; the eyelids help.

Citation: Daniel Smilek, Jonathan S.A. Carriere, J. Allan Cheyne, 'Out of Mind, Out of Sight Eye Blinking as Indicator and Embodiment of Mind Wandering', Psychological Science, April 2010; doi: 10.1177/0956797610368063