I have found the spiral dynamics value systems model (Beck & Cowan 2005) an interesting heuristic model but I was struggling to find scientific evidence for its validity. [e.g. The Inglehart-Welzel model (Inglehart & Wezel 2010) from traditional to secular/rational societies seems to correlate the blue to orange value system shift in spiral dynamics but no formal connection has been establised.]
Would you know studies which would back the spiral dynamics model?
If not, would you know better models of human value systems and how they evolve?