There is this social context of race relations whose grammar he is also learning, and I would just remind you of the passage where he starts to ask his mother about whether his granny is white or not.

一种来自家庭无可绘状的影响,当时社会的种族对立，对他学习的语言也有很深的影响,各位看一下当他问母亲,祖母是白人还是黑人？

耶鲁公开课 - 1945年后的美国小说课程节选