Monster Mothers

     When Harry Harlow completed his cloth mother experiments, he concluded that “mother love is indispensable”, and that it provides the infant a safe haven from which to explore an often dangerous world.  He also became interested in exploring the limits of that love.

“Knowing that a mother could give an infant love and security, we thought many years ago that we could produce anaclitic (dependency) depression by allowing baby monkeys to attach to cloth surrogate mothers who could become monsters.”

     Harlow built four monster mothers, all modified cloth mothers.  The first would blast the clinging baby with highly pressurized air.  “It would blow the animal’s skin practically off its body”, he wrote.

     The second mother would shake so hard that “the baby’s head and teeth would rattle”.  Neither of the first two monster mothers were able to dissuade their babies; the little monkeys “simply clung tighter and tighter to the mother, because a frightened infant clings to its mother at all costs.”

     The third mother had a wire frame embedded in its body; the experimenter would release the frame, which would thrust out suddenly and propel the infant off its mother.  The fourth mother Harlow called the ‘porcupine mother’: she would eject brass ‘spikes’ (which were dulled) all over her body, again compelling the infant to release her hold.

     While these second two mothers were able to literally force their babies to relinquish their hold on them, neither induced Harlow’s desired ‘psychopathology’; the babies would simply wait for the offending apparatus to recede back into its mother’s body, and then cling to her again.  Harlow was unsurprised by this result; he wrote, “the only recourse of an injured or rebuked child – monkey or human – is to make intimate contact with the mother at any cost.”

     Harlow did eventually succeed in inducing psychopathology in monkeys, through social isolation.  By taking infant female monkeys and keeping them in total isolation for the first six to nine months of their lives, he created adult female monkeys two-thirds of whom “turned out to be inadequate or evil mothers”.  Evil is not a word often applied to non-human animals; Harlow uses it repeatedly and deliberately.  These mothers might completely ignore their babies; worse, many of them displayed behaviors that were “brutal or lethal” towards their young.  They would crush the baby’s head in their teeth, or they would smash the baby’s head against the ground and drag it along the floor of the cage.

Evil Mother - Harlow

     Harlow may have caused psychopathology, but he couldn’t exterminate mother love.  The infants of these evil mothers “never gave up unless they were killed.  The babies went back and back and back to their mothers, trying forever to attach”.  If the baby survived, this often worked:

“In a manner of speaking, the infants healed the mothers.  And these mothers, who eventually became maternalized by their first babies, were, on the second, third, or fourth pregnancies, for all practical purposes, perfectly normal mothers.”

Image taken from Harlow’s 1970 paper, ‘Induced Psychopathology in Monkeys’

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.

‘The Nature of Love’

     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.

Wire and Cloth Mothers

     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”.

Open Field Without Mother

     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”.

Baby with Cloth Mother

     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.