Given the lack of a control group of hikers who were given access to technology or a group of technology users subjected to exercising indoors, I am not sure if the increase in attentional performance can be attributed to exposure to a natural environment. Plenty of research supports an increase in cognitive performance due to exercise. Thankfully the authors admit there are limitations of the study. A control for the effect of exercise would be fairly easy to pursue in the future and would significantly reduce the limitations of the study, making it easier to interpret (especially since the effect of exercise is likely to be the cause of the increase high-level executive functioning seen in this experiment).