Table 1.

Knowledge gaps.

Pathway	Knowledge Gaps
Sound	Which kinds of nature sounds are important; studies with visually-impaired individuals
Smell	Study of smells emitted directly from plants; in situ studies; how natural smells affect preferences and memory
Taste	Emotional effects of eating natural food; ability to distinguish natural food; cognitive effects of diet
Touch	Non-animal nature touch; effects of petting different kinds of animals; touch-specific studies
Phytoncides	Field studies; documenting fine-scale environmental distribution; how much is released from greenery, variation among plant species
Negative Air Ions	Replicate and improve studies; environmental distribution; release from greenery; correlation between benefits and sensitivity
Microorganisms	Relatively well-researched; connect variation in nature experiences with variation in microbiota