In 1958, Harry Harlow gave the Address of the President to the 66th Annual Convention of the American Psychological Association. The speech, called ‘The Nature of Love’, outlined for the first time Harlow’s now-famous ‘cloth mother’ experiments.
“The position commonly held by psychologists and sociologists is quite clear: the basic motives are, for the most part, the primary drives — particularly hunger, thirst, elimination, and sex — and all other motives, including love and affection, are derived or secondary drives”, explained Harlow. However, he found this explanation, that infants attach to their mothers for the sake of food alone, insufficient to explain the “lifelong, unrelenting persistence” of a child’s affection for its parent.
Harlow’s experiment was elegant, if heart-rending: he took eight newborn rhesus macaque monkeys, and gave them each a choice. Alone in their cages with them were two surrogate mothers. Both had cylindrical wire-mesh frames, enclosed a light bulb to create a radiating warmth, and had affixed to them repulsive croquet-ball faces with bicycle-reflector eyes. One of the mothers, however, was wrapped in sponge rubber and terry cloth. This was the ‘cloth mother’; the other mother was left with her wire innards exposed, the ‘wire mother’. In four of the cages, the wire mother held the food bottle; in the other four, the cloth mother.
If infant love is based on food production, Harlow reasoned, the babies should prefer whichever mother held the bottle. They did not. The baby monkeys overwhelmingly preferred the cloth mother, spending as much as eighteen to twenty-three hours a day clutching and rubbing her. If the cloth mother held the bottle, the babies ignored the wire mother completely; if the wire mother held the bottle, the little monkeys would dash over to her to feed, and then dash back to the cloth mother, curling around her for support. If the babies were separated from their cloth mother, they would “rush to the center of the room where the mother was customarily placed and then run rapidly from object to object, screaming and crying all the while.” The wire mother could not pacify them. They would rock and cry, wrapping their arms around themselves: “continuous, frantic clutching of their bodies was very common”.
If the cloth mother was replaced, “the babies rushed to her, climbed up, clung tightly to her, and rubbed their heads and faces against her body”.
Harlow compared the behavior of these monkeys with two babies whom he allowed to stay with their biological, monkey mothers. He concluded that “love for the real mother and love for the surrogate mother appear to be very similar…whether the mother is real or a cloth surrogate, there does develop a deep and abiding bond between mother and child.”
He concluded his talk with a persuasive and poignant anecdote. The first baby monkey intended for the surrogate mother experiment was born a month earlier than they had expected, and they had not yet completed construction of the surrogates’ faces. The head then placed on this monkey’s cloth mother was featureless; it was simply a ball of wood. The baby was left with this faceless mother for 180 days, at which point the experimenters replaced both surrogates’ heads with decorated ones.
“To our surprise the animal would compulsively rotate both faces 180 degrees so that it viewed only a round, smooth face and never the painted, ornamented face. Furthermore, it would do this as long as the patience of the experimenter in reorienting the faces persisted. The monkey showed no fear or anxiety, but it showed unlimited persistence.”
She wanted the face of her mother, blank or not. As Harlow would later put it, “a mother’s face that will stop a clock will not stop a baby”.
Images are all taken from Harlow’s ‘The Nature of Love’ speech, and were shown at the speech itself.
For a very good scientific biography of Harlow and explanation of his social and scientific context, read Deborah Blum’s Love at Goon Park: Harry Harlow and the Science of Affection.