It has been known for decades that infants up to 14 months old will act on altruistic impulses without reward.
Recent research, following on from a similar 1973 study, is starting to show that rewards could be responsible for the inhibition of this natural desire to help others—an innate altruism.
48 German toddlers averaging 20 months of age [were placed] in a room (one at a time) with a parent and an experimenter who sat at a table in the corner, apparently doing an unrelated task like placing balls in a basket or clipping napkins together. The experimenter pretended to accidentally drop one of the objects on the floor, and reached for it while looking at the toddler, waiting up to 30 seconds for the toddler to help her by picking it up. Eight of the children refused to leave their parent, and ten didn’t complete the task, but 36 became reliable helpers, returning the object to the experimenter 5 times.
The second phase of the experiment—conducted on these 36 children, each split into various reward/non-reward groups—discovered that those receiving rewards “helped the experimenter significantly less often than either the group that received only praise or the group that received no praise” if the reward was withdrawn.
As Dave Munger asks, Was it the reward, or the betrayal that caused the child’s behavior to change?