Workplace bullying occurs when an employee experiences a persistent pattern of mistreatment from others in the workplace that causes harm. It can include such tactics as verbal, nonverbal, psychological, physical abuse and humiliation. This type of workplace aggression is particularly difficult because, unlike the typical school bully, workplace bullies often operate within the established rules and policies of their organization and their society. In the majority of cases, bullying in the workplace is reported as having been by someone in authority over the target. However, bullies can also be peers, and occasionally subordinates. Research has also investigated the impact of the larger organizational context on bullying as well as the group-level processes that impact on the incidence and maintenance of bullying behaviour. Bullying can be covert or overt. It may be missed by superiors; it may be known by many throughout the organization. Negative effects are not limited to the targeted individuals, and may lead to a decline in employee morale and a change in organizational culture.