Scientists have known for some time that the human brain's ability to stay calm and focused is limited and can be overwhelmed by the constant noise and hectic, jangling demands of city living, sometimes resulting in a condition informally known as brain fatigue.

With brain fatigue, you are easily distracted, forgetful and mentally flighty. But an innovative new study from Scotland suggests that you can ease it simply by strolling through a leafy park.

The idea that visiting parks or tree-filled plazas lessens stress and improves concentration is not new. Researchers have long theorized that green spaces are calming, requiring less of our so-called directed mental attention than busy, urban streets do. Natural settings invoke "soft fascination," a beguiling term for quiet contemplation, during which directed attention is barely called upon and the brain can reset those overstretched resources.

The theory, while agreeable, has been difficult to put to the test. Previous studies have found that people who live near trees and parks have lower levels of cortisol, a stress hormone, in their saliva than those who live primarily amid concrete, and that children with attention deficits tend to concentrate and perform better on cognitive tests after walking through parks or arboretums.

But it had not been possible to study the brains of people while they were actually outside, moving through the city and the parks. At least not until the recent development of a lightweight, portable version of the electroencephalogram, a technology that studies brain wave patterns.

For the new study, published last month in the British Journal of Sports Medicine, researchers at Heriot-Watt University in Edinburgh and the University of Edinburgh attached the portable EEGs to the scalps of 12 healthy young adults. The electrodes, hidden beneath a fabric cap, sent brain wave readings wirelessly to a laptop carried in a backpack by each volunteer.

The researchers, who had studied the cognitive effect of green spaces for some time, sent each volunteer out on a walk of about a mile and half that wound through three different sections of Edinburgh.

What they found confirmed the idea that green spaces lessen brain fatigue.

When the volunteers made their way through busy, urbanized areas, particularly the heavily trafficked district at the end of the walk, their brain wave patterns consistently showed they were more aroused and frustrated than when they walked in the parkland, where brain-wave readings became more meditative.