works simulators are not very accurate so there is a problem of sort of transferring from simulation to the real world it's got to be to work on this but it's a big mystery there which I'll come back to in the second half of the talk and the mystery is is how is it that humans can learn to drive a car in about 20 hours of training without causing any accident and the sort of preview of the answer to this is that we have internal predictive models of the world that allows us to predict that if we drive near a cliff