When a person's mind wanders, they are not paying attention to what is directly in front of them. Now researchers from the University of Waterloo in Canada have the body reacts in the same way.
They found those who were not paying attention blinked more, setting up a tiny physical barrier between themselves and the outside world.
Are you listening to me? Scientists find blinking eyes show if the mind the wandered
Is your partner really listening? How often they blink is a telling sign. (Posed by models)
Cognitive neuroscientist Daniel Smilek, of the University of Waterloo, studies how people pay attention - and don't.
For this study, he was inspired by brain research that shows, when the mind wanders, the parts of the brain that process external goings-on are less active.
'And we thought, ok, if that's the case, maybe we'd see that the body would start to do things to prevent the brain from receiving external information,' Professor Smilek says.
'The simplest thing that might happen is you might close your eyes more.'
So Professor Smilek and his team set out to look at how often people blink when their mind wanders.
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, the team reports in Psychological Science, a journal of the Association for Psychological Science.
'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,' said Professor Smilek.
He said this is part of a shift in how scientists are thinking about the mind.
'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,' he said.
The mind doesn't ignore the world all by itself; the eyelids help. So if your boyfriend is fluttering his lids during a conversation, chances are he's thinking about Match of the Day. ( dailymail.co.uk )