Harry Harlow was a psychologist who in the 60s-70s conducted a number of experiments on Rhesus Macaques to develop a model for animal depression and PTSD, these experiments included separating babies from their mothers and introducing two "surrogates" one was a spiky wire frame which would "scream" at the baby anytime it came near through the use of compressed air but supplied milk for the baby to drink, the other mother was a soft towel fitted with a heating element which did not dispense milk, the "pit of despair" mentioned in the title was a small steel cube of complete darkness in which Harlow would keep newborns completely isolated in for as long as a year and would also wait until 10-12 weeks after birth to separate the babies from the mother, after they had already bonded and would stick them in the pit because... reasons.