ReviewThe effects of preferred natural stimuli on humans' affective states, physiological stress and mental health, and the potential implications for well-being in captive animals

- Humans often like and benefit from certain natural stimuli and environments.
- Benefits include reduced stress, and improved mood, physical and mental health.
- These effects do not seem to depend on early experience or culture.
- Natural stimuli may also benefit animals kept in anthropogenic environments.
- More research is needed to clarify the potential animal welfare implications.

Exposure to certain natural stimuli improves people's moods, reduces stress, enhances stress resilience, and promotes mental and physical health. Laboratory studies and real estate prices also reveal that humans prefer environments containing a broad range of natural stimuli. Potential mediators of these outcomes include: 1) therapeutic effects of specific natural products; 2) positive affective responses to stimuli that signalled safety and resources to our evolutionary ancestors; 3) attraction to environments that satisfy innate needs to explore and understand; and 4) ease of sensory processing, due to the stimuli's “evolutionary familiarity” and/or their fractal, self-repeating properties. These processes, and the benefits humans gain from natural stimuli, seem to be largely innate. They thus have strong implications for other species (including laboratory, farm and zoo animals living in environments devoid of natural stimuli), suggesting that they too may have nature-related “sensory needs”. By promoting positive affect and stress resilience, preferred natural stimuli (including views, sounds and odours) could therefore potentially provide effective and efficient ways to improve captive animal well-being.