"Based on both empirical and theoretical evidence, Zapf (1999a) categorised five main types of bullying behaviour: 1 work-related bullying which may include changing the victim's work tasks in some negative way or making them difficult to perform; 2 social isolation by not communicating with somebody or excluding someone from social events; 3 personal attacks or attacks on someone's private life by ridicule or insulting remarks or the like; 4 verbal threats in which somebody is criticised, yelled at or humiliated in public;and 5 spreading rumors."