12 months ago
It's interesting how often questions about series show up on aptitude tests for kids. Presumably because the subject isn't taught in schools till much later, so there's some hope of creating questions that measure ability rather than knowledge.
You'd get the impression from looking at IQ/aptitude tests that identifying series is somehow intrinsic to intelligence, but really the only reason such questions work, to the extent they do, is customs about what gets taught at what age.
The main thing I've learned from looking at such tests is how hard it must be for the test designers to create questions that measure ability rather than knowledge. They have very little room (possibly zero room) to maneuver. Which in turn explains Mensa.