In a 1959 experiment, monkeys were separated from their mothers at birth. All of the monkeys received feedings from a wire monkey holding a bottle. Some monkeys were fed by bare wire models, but others received their feedings from models covered with warm terry cloth. The monkeys with a bare wire mother only approached it when hungry. The monkeys with the terry cloth mother clung to it while eating and ran to it when frightened or stressed. Moreover, the monkeys with the terry cloth mother were more likely to thrive. Which theory of emotional development does this study support?
