The article mentions some research. Let me add https://en.wikipedia.org/wiki/Harry_Harlow#Partial_and_total_isolation_of_infant_monkeys https://en.wikipedia.org

The article mentions some research. Let me add https://en.wikipedia.org/wiki/Harry_Harlow#Partial_and_total_isolation_of_infant_monkeys https://en.wikipedia.org/wiki/Harry_Harlow#Partial_and_total... to the list: "Partial isolation involved raising monkeys in bare wire cages that allowed them to see, smell, and hear other monkeys, but provided no opportunity for physical contact. [..] partial isolation resulted in various abnormalities such as blank staring, stereotyped repetitive circling in their cages, and self-mutilation."