How big a role does survivorship bias play? It seemed like in the case of chimpanzees the article sort of implies that the effect "nice and more self-controlled

How big a role does survivorship bias play? It seemed like in the case of chimpanzees the article sort of implies that the effect "nice and more self-controlled chimpanzees live longer", mattered too? I wonder what portion of "older people being more emotionally balanced" can be explained by more emotionally balanced people surviving longer in Western society? Sounds like something somebody will have tried to quantify at least in terms of the order of magnitude?