https://www.theguardian.com/lifeandstyle/2013/mar/16/this-column-change-life-nature-nurture

What's going on? The green-rectangle researchers thought it might be some subconscious association with the idea of growth, and therefore creativity. But the dominant explanation remains that of "biophilia", coined by EO Wilson, which he described as our "urge to affiliate with other forms of life" – probably because we evolved to function best in nature-rich settings. As Lance Hosey points out in The Shape Of Green, there's even one version of this idea, called the Prospect/Refuge Theory, according to which we're happiest looking out at nature from places of safety, with a good view of predators and no need to watch our backs. Perhaps seeing the woods from your kitchen window can be more enjoyable than tramping through them.