Farrington et al (2001) reviewed 6 different explanations for why offending and antisocial behaviour were concentrated in families and transmitted from one generation to the next. First, there may be intergenerational continuities in exposure to multiple risk factors, such as poverty, disrupted families, and living in deprived neighbourhoods. Second, assortative mating (for example, the tendency of antisocial females to choose antisocial males as partners) facilitates the intergenerational transmission of offending. Third, family members may influence each other (for example, older siblings may encourage younger ones to be antisocial). Fourth, the effect of a criminal parent on a child’s offending may be mediated by environmental mechanisms, such as poor parental supervision and inconsistent discipline. Fifth, intergenerational transmission may be mediated by genetic mechanisms. Sixth, there may be labelling and police bias against known criminal families.