What is successful ageing? Current opinion is that “cognitive vitality is essential to quality of life…in old age.” 1 This depends substantially on people's cognitive ability from early life, 2 and on how much they decline from their cognitive peak in young adulthood. Early cognitive ability also affects physical health and even survival to old age. 2 But surely happiness and satisfaction with life are also key indices of successful ageing. Happiness was described as “the highest good and ultimate motivation for human action” 3; this does not seem to be related to current cognitive ability. 3 Cognitive level in youth and the amount of cognitive change across the lifespan are important indicators of cognitive vitality in old age. We examined a unique data set to investigate whether these factors are associated with people being happier.