Look! Those wonderful neuroscientists are at it again, showing that different parts of the brain are active when we weigh up healthy but not tasty v. unhealthy buttasty foods. People whose 'angel' (bad name, I know, but let's leave it for now) bit of the brain did not 'speak up loudly enough' (unpick that metaphor...) when shown a choice between something neutral and something tasty but unhealthy tended to choose the latter. Poor akratic souls. Maybe Plato was right about distinctly located centres of motivation. Or perhaps not.