Many variables influence how children develop relationships and how well their interaction styles work for harmony in relationships. Infants younger than 1 year were observed to choose animal puppets they have observed helping rather than hindering another puppet. Toddlers show clear abilities to help others.

Some factors are fundamental for the mature development of empathy, sharing, cooperation, and helpfulness. Early primate research revealed that maternal love is crucial for later peer relationships. During the 1950s, Harry Harlow and Robert Zimmerman reared baby monkeys with one artificial mom covered in soft terrycloth and one of wire with a nippled bottle providing milk. Monkeys clung constantly to soft cloth moms unless they needed a swig of milk. These isolated monkeys bit themselves, rocked compulsively, and could not play ...