"The duration of the bullying seems to be closely related to the frequency of bullying, with those bullied regularly reporting a longer duration of their experience than those bullied less frequently (Einarsen and Skogstad, 1996). This seems to be in line with a model of bullying highlighting the importance of conflict-escalation, with the conflict becoming more intense and more personalised over time (Zapf and Gross, 2001). The negative and unwanted nature of the behaviour involves is essential to the concept of bullying. Victims are exposed to persistent insults or offensive remarks, persistent criticism, personal or, even in some few cases, physical abuse (Einarsen, 200b). Others experience social exclusion and isolation; that is they are given the 'silent treatment' or 'sent to Coventry' (Williams, 1997). These behaviours are 'used with the aim or at least the effect of persistently humiliating, intimidating, frightening or punishing the victim' (Einarsen, 2000b, p. 8)."