Why does walking clear your head? What the research says

A walk can help with some kinds of thinking, and the samples are small. A 50- to 55-minute arboretum walk improved a working-memory test more than the same kind of walk downtown. A later review found support for working memory after time in natural settings, with low to moderate effects, and less consistent results on other attention tests. A 90-minute nature walk, and not a walk on a busy road, left people less caught going round in circles on the same thought. Walking also helps people come up with many ideas. It does not help a problem that has one right answer.

Berman, Jonides, and Kaplan (2008) asked 38 University of Michigan students to walk both the Ann Arbor Arboretum and downtown. Each walk was 50 to 55 minutes and 2.8 miles. Everyone did both, a week apart, so the comparison is within the same person. Before each walk they had already done a tiring memory task. Afterwards they repeated a backwards digit-span test: hear numbers and say them in reverse.

The score rose more after the arboretum than after downtown, about 1.5 digits against about 0.5 (from 7.90 to 9.40, versus 7.90 to 8.40). The nature improvement was reliable. The downtown improvement was not. One person was left out of that comparison because their first score was extremely low, so the test is 37 people, not 38. Season did not change the result, and a shift in mood did not track the memory score.

That is a difference on one test, in students, on a set route, after attention had already been worn down. A second experiment in the same paper used pictures instead of a walk, with 12 people, and the interaction on this memory test was not reliable. The walk is the result that fits the question.

Stevenson, Schilhab, and Bentsen (2018) reviewed 42 articles published since July 2013, with 49 outcome measures across eight kinds of test. Working memory and cognitive flexibility tended to improve, with low to moderate effects. Attentional control improved less reliably. Whether people arrived already tired made less of a difference than a simple story would predict, and the authors call that part less clear. An earlier review had already found the directed-attention account ambiguous.

Later work on working memory points in a similar direction. The support is not even, and the review does not include the 2008 walk, which falls outside the years it covered.

Bratman et al. (2015) randomly assigned 38 healthy adults to a 90-minute walk. Nineteen walked in grassland with scattered oaks near Stanford. Nineteen walked a busy road in Palo Alto. The questionnaire asks how much a person keeps going round in circles on the same thought, the pattern researchers call rumination. Scores fell in the nature group and did not change in the road group.

That questionnaire result is weaker than it is often retold. The overall comparison of the two groups was only at P = 0.07. The drop inside the nature group was reliable, on 18 of those people. Activity in the subgenual prefrontal cortex fell in the nature group and not in the road group, and that interaction was clear, on fewer people than the 38 who were assigned. It is one experiment, and one comparison of two routes.

Oppezzo and Schwartz (2014) asked whether walking changes the kind of thinking, not only the setting. In the first experiment, 48 people sat and then walked on a treadmill. On a task that asks for many uses of an ordinary object, 81% scored higher while walking. On a task with one right answer, only 23% improved, and the group did mildly worse while walking. A later experiment found a similar lift for generating ideas outdoors. The benefit was for coming up with options, not for narrowing to one answer.

The 81% figure is a treadmill, indoors. It is not a park, and it is not a measure of a quiet mind. The outdoor experiments are on walking and creativity.

Oppezzo and Schwartz measured ideas during a walk and shortly after, not whether a person feels clear an hour later. Stevenson and colleagues found working memory and flexible thinking more often than a general attention effect. A walk can help a tired memory test, a repetitive thought, or a list of ideas. It does not show that walking makes thinking clear in general.