Who studied baby monkeys to demonstrate the importance of "contact comfort"?

Harry Harlow conducted famous experiments with baby rhesus monkeys to investigate the concept of "contact comfort." In his studies during the 1950s, Harlow provided infant monkeys with two surrogate mothers: one made of wire that provided food, and another made of soft cloth that offered no food. He observed that the baby monkeys overwhelmingly preferred to spend time with the cloth mother, seeking comfort and security over the bare necessity of food from the wire mother. This preference highlighted the significance of tactile and emotional comfort in attachment, challenging previous beliefs that attachment was primarily based on feeding. Harlow's research was pivotal in understanding the emotional bonds that develop between infants and their caregivers, contributing to attachment theory and influencing practices in child development and psychology.