Prosocial behavior is defined as voluntary behavior intended to benefit another person. It includes helpful and altruistic acts according to social norms. Research on bystander intervention in emergencies found that the presence of other bystanders decreases the likelihood of any one person helping (the bystander effect). Latane and Darley identified five decision points people go through when deciding whether to help: noticing the emergency, defining it as such, taking responsibility, planning a response, and acting. Factors like ambiguity, mood, gender, attractiveness, and weather influence bystander intervention.