Who are the subjects of psychology research?

What impact does it have on psychology research, that the vast majority of subjects are from Western, Educated, Industrialised, Rich and Democratic (WEIRD) countries? Vagina Dentata has posted a really interesting analysis of this, based on some recent research.

Probably the most striking point for me:

A recent analysis of the top journals in six sub-disciplines of Psychology from 2003-2007 revealed that 68% of subjects came from the US, and 96% of subjects were from Western industrialised countries, specifically North America, Europe, Australia, and Israel (Arnett, 2008) reflecting the academics country of residence.

This means that 96% of psychological samples come from countries with only 12% of the world’s population.