Critical period (second language acquisition) ; Alter (Einfluss auf Zweitspracherwerb) ; Age (influence on second language acquisition) ; Ultimate attainment (second language acquisition) ; Near-native competence (second language acquisition) ; AoA; Age of acquisition (second language acquisition) ; Sensitive period (second language acquisition) ; Speech perception (second language acquisition) ; Sprachperzeption (Zweitspracherwerb) ; Speech production/speech perception (second language acquisition)