Sapiens: A Brief History of Humankind

by Yuval Noah Harari

The truth of this theory has been known at least since the 1950s, when the American psychologist Harry Harlow studied the development of monkeys. Harlow separated infant monkeys from their mothers several hours after birth. The monkeys were isolated inside cages, and then raised by dummy mothers. In each cage, Harlow placed two dummy mothers. One was made of metal wires, and was fitted with a milk bottle from which the infant monkey could suck. The other was made of wood covered with cloth, which made it resemble a real monkey mother, but it provided the infant monkey with no material sustenance whatsoever. It was assumed that the infants would cling to the nourishing metal mother rather than to the barren cloth one. 42. One of Harlow’s orphaned monkeys clings to the cloth mother even while sucking milk from the metal mother. To Harlow’s surprise, the infant monkeys showed a marked preference for the cloth mother, spending most of their time with her. When the two mothers were placed in close proximity, the infants held on to the cloth mother even while they reached over to suck milk from the metal mother. Harlow suspected that perhaps the infants did so because they were cold. So he fitted an electric bulb inside the wire mother, which now radiated heat. Most of the monkeys, except for the very young ones, continued to prefer the cloth mother. Follow-up research showed that Harlow’s orphaned monkeys grew up to be emotionally disturbed even though they had received all the...

Could be the reason for anxiety and emotional disturbances in humans - lack of love and care in early stages of life