Meditating monks are giving clues about how the brain's basic responses can be overridden, researchers say.
The researchers studied Tibetan Buddhist monks
Australian scientists gave Buddhist monks vision tests, where each eye was concurrently shown a different image.
Most people's attention would automatically fluctuate - but the monks were able to focus on just one image.
Writing in Current Biology, the scientists say their ability to override this basic mental response indicates how the brain can be trained.
Researchers from the University of Queensland and the University of California, Berkley, studied 76 Tibetan Buddhist monks at mountain retreats in India.
The monks had undergone between five and 54 years of meditative training.
In the tests, they were given special goggles that meant they could see a different image with each eye.
Normally, the brain would rapidly alternate between both - termed perceptual or visual rivalry.
It had been thought that this was a basic and involuntary response.
However, the monks - who carried out "one-point" meditation, where they focus attention on a single object or thought - were able to focus on one image.
Monks who had undergone the longest and most intense meditative training were able to focus their attention on just one of the images for up to 12 minutes.
Olivia Carter, of the University of Queensland, said: "The monks showed they were able to block out external information.
"This is an initial step in understanding how their brains work.
"It would now be good to carry out further tests using imaging techniques to see exactly what the differences are in the brains of the monks."
She said that could direct researchers to a broader understanding of how meditation influences what happens in the brain when someone is deciding whether to give something their attention, and what happens when they choose not to dwell on bad news, or to calm down.
Ms Carter added: "Buddhist monks often report that if something negative happens they are able to digest it and move on.
"People who use meditation, including the Dalai Lama have said that the ability to control and direct your thoughts can be very beneficial in terms of mental health."
Dr Toby Collins, of the Oxford Centre for the Science of the Mind, told the BBC News website: "Meditation is a way of tapping into a process of manipulating brain activity."
He said the idea that meditation trained the brain to attend to just one thing at a time fitted in with previous research.
He added: "How that's done, we don't yet know. But studies using fMRI (functional magnetic resonance imaging) can show what's happening in the brain."