The Broadened and Built Theory in Psychology

The theory I'm thinking of we've talked a little bit about before steven is called broadened and built. The theory that barber fredrickson a psychologist I admire a lot that she came up with for why? Why evolutionarily speaking functionally speaking why we have happiness like why did human beings Evolve to have positive emotions joy laughter Satisfaction gratitude and so forth. It's a funny thing to ask because now the science of happiness has been somewhat popularized But not that long ago.