《葛传槼英语惯用法词典》有如下解释：

Is that...? Do you...? Can't I...?等的否定式在正式英语里和口语里不同：在正式英语里用Is that not...? Do you not...? Can I not...?或Cannot I ...?等。在口语里，用Isn't it...? Don't you...? Can't I...?等。

相当于Am I not...?的口语有Ain't I...? An't I...?和Aren't I...?有人以为都是不正当的，似乎Aren't I ...?最为人所反对。