UG; Universal grammar ; Functional category (second language acquisition) ; Funktionale Kategorie (Spracherwerb) ; Funktionale Kategorie (Zweitspracherwerb) ; Comparison ; Second language acquisition (psycholing.) ; Transfer (second language acquisition) ; Transfer (Zweitspracherwerb) ; Cross-linguistic influence (second language acquisition) ; Interference (second language acquisition) ; Triggering (second language acquisition) ; Parametrization (second language acquisition) ; Second language acquisition in children; Kindlicher Zweitspracherwerb; Child second language acquisition ; Syntax, contrastive; Syntax, kontrastive; Contrastive syntax ; Questions; Interrogative sentence ; Yes-no question; Polar question ; W-Frage; Konstituentenfrage; Wh-question ; Subject-auxiliary inversion; SAI; Stylistic inversion ; English ; Japanese