Why did baby monkeys cling to a cloth mother instead of the one with milk?
In the 1950s, a psychologist offered baby monkeys a wire mother with milk or a soft cloth mother with none. The babies mostly chose softness.
▶ Start the storyBecause for a baby monkey, being held mattered more than being fed. Harry Harlow's experiments tested what makes a baby attach to its mother, and the answer was not milk.
At the time, feeding was thought to be the most important factor in forming a mother-child bond, and physical contact with infants was considered harmful, which led to contact-less nurseries. John Bowlby disagreed: a mother, he claimed, provides much more than food. Harlow set out to test this with infant rhesus monkeys, building surrogate mothers from wire and wood. One was bare wire; the other was covered in cloth. In one setup the wire mother held the milk bottle, and in the other the cloth mother did.
Wire mother
- Bare wire and wood
- Held the bottle in one setup
- Visited only to feed
Cloth mother
- Covered in cloth
- Held the bottle in the other setup
- Clung to, with or without milk
Overwhelmingly, the babies clung to the cloth mother. Even when only the wire mother had milk, they visited her only to feed. Harlow concluded that there was much more to the mother-infant relationship than milk, and that this "contact comfort" was essential to the psychological development and health of infant monkeys and children.
The cloth mother also acted as a secure base. Infants used the surrogate as a base for exploration and as a source of comfort in novel and frightening situations. Faced with a frightening toy, infants without their surrogate cowered, but with it they did not show great fear and often explored it.
The work remains controversial. Many of Harlow's experiments are now considered unethical, and they helped propel today's ethics regulations. Critics also note that clinging is a matter of survival in young rhesus monkeys but not in humans, so conclusions may overstate the importance of contact comfort for people.
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Recap
Infant monkeys chose contact comfort over food, so a bond is more than a meal, though results from monkeys may not map exactly onto humans.
💡 A trick to remember it · Soft beats snack: the babies ran to the cuddle and only popped over for lunch.
Surprising fact · Monkeys with only a wire mother had trouble digesting milk, which Harlow read as stress from lacking contact comfort.
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No source, no claim. Every fact in this lesson (16 claims) cites at least one of these.