This is a brand new theory which says that the lack of contact with nature creates behavioral problems in children and, later, in adults. I've been reading about this and different variations of the theory for years now (i.e. biophilia) and firmly believe in it not only for humans but, most especially for our parrots, making it the number one reason why I try to hard to give them a life as close as possible to what they would have in the wild (natural perches, toys made out of natural materials, companion of their own species, flight, solar schedule, etc - even the colors I use to paint the walls!).
https://www.onegreenplanet.org/environm ... proven-it/
https://en.wikipedia.org/wiki/Nature_deficit_disorder
https://science.howstuffworks.com/life/ ... eople6.htm