Environmental psychologists, Stephen and Rachel Kaplan, conducted a 9-year study for the U.S. Forest Service in which they took groups of people on discovery trips out into the wild for two weeks at a time. During the treks and afterward, subjects reported experiencing a sense of peace and an ability to think more clearly. They also reported that just being in nature was more restorative than any of the specific physically challenging activities, such as rock climbing, for which such programs are mainly known.
The Problem - Mental Fatigue
According to the Kaplans' research, too much directed attention leads to what they call "directed-attention fatigue", and it's marked by impulsive behavior, agitation, irritation, and inability to concentrate. They say it occurs mainly because neural inhibitory mechanisms become fatigued by blocking competing stimuli. In other words, your mind becomes like the Chinese acrobat's trick of spinning multiple plates on sticks. As long as she can keep all the plates spinning everything's fine. But the moment she stops or slows down they all come crashing down. Here's another way of describing it. Your mind is like a system of roads and traffic patterns. Ordinarily your brain has the ability to act as a traffic cop directing certain flows of thought but not all at once. Directed-attention fatigue is like a traffic jam - all lines of thought are demanding focus all at the same time. Or it's like too many plates spinning on sticks. Your brain gets tired and bad things begin to happen - cognitive ability goes down, you respond negatively and emotionally to the stress, you can't focus.
The Solution - Attention Restoration
The amazing connection that the Kaplans discovered is that being out in the great outdoors is like pressing the reset button. "If you can find an environment where the attention is automatic, you allow directed attention to rest. And that means being in an environment that's strong on fascination. Nature can be the most effective source of such restorative relief."
So instead of having to actively concentrate on reading, organizing, comprehending what someone else is saying, being outside where you encounter something really big (like breathtaking scenery) or something really small and delicate (like a snowflake, pinecone, or flower) your mind is captured by it - the focus is complete and automatic. It's not fragmented by a hundred different competing thoughts. And it's that unity of thought that is therapeutic.
Double the Benefit
When you couple this kind of attention-restoration with human movement that's when you experience a complete mental and emotional overhaul. Part of the benefits of cardio-respiratory exercise include mental alertness, reduced tendency toward depression and anxiety, improved tolerance to stress, and improved relaxation and sleep.
We were made to respond to the natural world. There's more that could be said on the effect of being surrounded by living things (as opposed to non-living) in the natural world, moving in it, using tactile senses to feel it, and even the specific effect of the color green, but we'll save that for another post. Suffice it to say, do yourself a favor and spend a Saturday exploring in the woods, beaches, canyons, or mountains and give your mind the break it desperately needs.