Self-expression values are part of a core value dimension in the modernization process. Self-expression is a cluster of values that include social toleration, life satisfaction, public expression and an aspiration to liberty. Ronald Inglehart, the University of Michigan professor who developed the theory of post-materialism, has worked extensively with this concept. On the Inglehart–Welzel Cultural Map self-expression values are contrasted with survival values, illustrating the changes in values across countries and generations. The idea that the world is moving towards self-expression values was discussed at length in an article in the Economist. Self expression is to say something that you truly believe is important in a form of communication, such as art, speech and dance. It is to reveal yourself in a way that is special to yourself.