> cognition test results are really only valid for people from the cultural context the test was written for. They're perfectly good for looking at changes ove

> cognition test results are really only valid for people from the cultural context the test was written for. They're perfectly good for looking at changes over time within a population, you just have to be careful doing between-population comparisons (whether a test is "valid" at that point depends what specific question you want to answer).