13:32The Why FactorGraffiti: Why do we do it?BBC World Service Duration: 18 minutes Mon 5th Oct 2015, 13:32 on BBC World ServiceAvailable for over a yearListen nowGraffiti is both an ancient and modern activity, but why do we do it? Show more GenresFactualScience & NatureFormatsDocumentariesBrandThe Why Factor Source: BBC Online