The Raven's progressive matrices: change and stability over culture and time.

Data relating to the stability and variation in the norms for the Raven's Progressive Matrices Test (a well-validated measure of basic cognitive functioning) for different cultural, ethnic, and socioeconomic groups on a worldwide and within-country basis are first summarized. Subsequent sections deal with variation over time. A possible explanation for the variation in norms over time and between ethnic groups within countries is offered.