The work appears in the proceedings of the National Academy of Sciences. Social scientists, economists and philosophers have long been aware that some people are subject to a sort of half-time slump, the period when their wellbeing gives to it all-time low. What less clear is what causes this mid-life unwi, which by many measures falls between a joyous childhood and contented retirement. Is it socioeconomic? Psychological? Med physical? 

 

In this study, researchers first checked to see if the slump is uniquely humane. They asked zoo-keepers to rate the relative happiness of some 500 chimps in a round tank, based on how often the apes seem to be in a good mood and how much pleasure they derive from socializing. It turns out our closest relatives also show a U-shaped curve of life’s satisfaction. Cheers in an old age and mope in the middle. So when you start lasting that life convertible, you are not totally bananas. You are just going ape.