Imagine playing Scrabble without being able to rearrange the tiles on your rack or designing a building without sketching ideas or making models. Such a thought exercise shows the importance of environmental interaction in human thinking. But many cognitive tests meant to predict real-world achievement measure only what people can process inside their head. A new type of IQ test that lets takers “externalize” their problem-solving predicts school grades better than the original version it was based on, a recent study found.