A walk in the park

I love it when science “proves” what we all know already – in this case that a walk in the park (or any quiet, green natural environment) makes you feel good.

But, to give the Stanford University researchers who came to this conclusion their due, there’s more to the story that that.

For example: They figured out how to measure the subjective sense of “feeling good.” It turns out that a particular part of the brain known as the subgenual prefrontal cortex shows increased activity during what cognitive scientists like to call “morbid rumination.” (The rest of us call this grumbling to ourselves and rehashing all the ways our lives suck.) When this part of our brain is less active, we are happier. We “feel good.”

And this interesting finding: It’s not the invigorating physical effect of walking that makes you “feel good” – that is, have decreased activity in the morbid rumination section of the brain. Research subjects who walked along a traffic-clogged street did not get the same neurological advantages and mood elevation as the park walkers.

Here are the details: Researchers gathered 38 healthy, adult city dwellers and asked them to complete a questionnaire to determine their normal level of morbid rumination. The researchers also checked for brain activity in each volunteer’s subgenual prefrontal cortex, using scans that track blood flow through the brain. (Greater blood flow to parts of the brain usually signals more activity in those areas.) Then the scientists randomly assigned half of the volunteers to walk for 90 minutes through a leafy, quiet, parklike portion of the Stanford campus or next to a loud, hectic, multi-lane highway in Palo Alto. The volunteers were not allowed to have companions or listen to music. They were allowed to walk at their own pace. Immediately after completing their walks, the volunteers returned to the lab and repeated both the questionnaire and the brain scan.

For the highway walkers, the blood flow to their subgenual prefrontal cortex was still high and their broodiness scores were unchanged. But the volunteers who had strolled along the quiet, tree-lined paths showed meaningful improvements in their mental health, according to their scores on the questionnaire. They also had less blood flow to the subgenual prefrontal cortex. That portion of their brains were quieter.

This little study joins a growing body of research investigating the effects of urban living. Various studies have found that urban dwellers with little access to green spaces have a higher incidence of psychological problems than people living near parks and that city dwellers who visit natural environments have lower levels of stress hormones immediately afterward than people who have not recently been outside.

It’s not only how you live but where you live.