disentanglement puzzle; wire puzzle
unexplained fever in an infant (in the past believed to be related to intellectual development); teething fever; (lit.) wisdom fever; fever that comes from using one's head too much
battle of wits; contest of wits
Chiezō (Japanese dictionary published by Asahi Shimbun)
having wisdom and resources; being clever and talented
wisdom and good (common sense) judgment
big heads have little wit
being too clever (for one's own good); getting done in by one's own cleverness
dissection puzzle (tangram, Sei Shonagon chie-no-ita, etc.)