The clinical characteristics of OCD include behavioural, emotional and cognitive symptoms. Behavioural characteristics include compulsions (e.g. excessive hand washing). Emotional characteristics include anxiety and distress caused by obsessions, which consist of persistent and/or forbidden thoughts. Cognitive characteristics include obsessive thoughts (obsessions), which are the main cognitive feature of OCD. Sufferers of OCD know that their obsessions and compulsions are irrational, and experience selective attention directed towards the anxiety-generating stimuli.