Final answer:
Gianna's action of helping her neighbor with the groceries out of a selfless desire to assist is an example of altruism, a type of prosocial behavior.
Step-by-step explanation:
The behavior that Gianna exhibited by helping her neighbor with the groceries would be called altruism. Altruism is considered a form of prosocial behavior characterized by selfless helping of others, without seeking personal gain or benefits. Although feeling good after helping can occur, researchers argue that it is a consequence rather than a cause of altruistic actions. Some researchers suggest that altruism operates on empathy, which is the capacity to understand and feel what another person is experiencing, leading to the desire to help.