Western, Educated, Industrialized, Rich, and Democratic – Henrich et al. pointed out that the vast majority of psychological studies use a very specific type of subject, not at all typical of the global population. IIndeed for many experiments the main subjects are psychology students! In a meta-analysis where studies had also been performed in cultural settings which were not WEIRD, they found that cognitive and perceptual results that had been thought to be fundamental to human nature, for example the Müller–Lyer illusion, turn out to vary between cultures.