English as a second language; ESL; TESOL ; Lernmotivation; Affekt (Einfluss auf Zweitspracherwerb) ; Affect (influence on second language acquisition) ; Motivation research ; Speech anxiety; Receiver apprehension; Communication apprehension ; Second language acquisition (pragm.) ; Zweitspracherwerb (pragm.) ; Interactionist hypothesis (second language acquisition) ; Conversational analysis (second language acquisition) ; Other varieties of English