Aunt Alexandra thinks Scout is "dull" (not clever). Why does she think this, and is she right?
Aunt Alexandria thinks Scout is dull because she doesn't have the basic knowledge of "society" that Alexandria feels she should. She doesn't always speak correctly, she gets in trouble at school, and she doesn't dress or act like a lady.
Scout is actually a very intelligent child, but she doesn't submit well to authority. She is loud and outspoken, and doesn't always understand the consequences of acting rashly. Atticus has taught Scout to think for herself, which is contrary to Alexandria's philosophy. Throughout the book, there is clear evidence of Scout's intelligence and maturing, as well as Alexandria's eventual understanding of Scout and Atticus.
Aunt Alexandra and Scout clash right away. Aunt Alexandra thinks that Scout is dull because she hasn't had a woman's influence in her life. Scout knows nothing of the way a lady should act in society. She disapproves of the way Scout acts and the things she says. Aunt Alexandra thinks she is dull because of the ways she passes her time. Scout has a hard time with her at first. She doesn't want anyone coming in and trying to tell her what to do.
"Aunt Alexandra was fanatical on the subject of my attire. I could not possibly hope to be a lady if I wore breeches; when I said I could do nothing in a dress, she said I wasn't supposed to be doing things that require pants. Aunt Alexandra's vision of my deportment involved playing with small stoves, tea sets, and wearing the Add-A-Pearl necklace she gave me when I was born; furthermore, I should be a ray of sunshine in my father's lonely life."
Scout is actually very clever. Atticus has treated her like an adult, so she understands things that Aunt Alexandra might think is not good for young girls. Aunt Alexandra was also raised in a time when women had a certain place in the family. She wants Scout to be raised with the ideals she was raised with, but Atticus wants more for his daughter. Scout and Aunt Alexandra come to care about each other, and to appreciate the differences in the two of them.
Aunt Alexandra does not actually come out and say that Scout is dull. The word "dull" is never used by Aunt Alexandra. In chapter 13, Scout says the following:
"It was plain that Aunty thought me dull in the extreme, because I once heard her tell Atticus that I was sluggish" (128).
The word "sluggish" has many definitions, and one is that a person is slow to respond. Sometimes, if a person seems slow to respond, people can misunderstand that as unintelligent or not clever. There are times when Jem, Scout, and Aunt Alexandra are talking about heredity and Jem needs to clarify the discussion for his sister's understanding. That might be where Aunt Alexandra thinks that Scout isn't clever. For example, in chapter 23, Scout says that she would like to invite Walter Cunningham over for a visit. She even suggests that he stay the night sometime. This ignites a fire under Aunt Alexandra and there is a discussion which seems to show that Scout doesn't understand what is going on. She asks why Walter can't play with her and Aunt Alexandra says the following:
"Because—he—is—trash, that's why you can't play with him. I'll not have you around him, picking up his habits and learning Lord-knows-what. You're enough of a problem to your father as it is" (225).
It's as if Aunt Alexandra slows down her speech so Scout can understand her more clearly. All Alexandra does, though, is establish her own bigotry and prejudices. It's not that Scout is dim-witted, because she's not. Scout just isn't prejudiced like her Aunt. She doesn't understand such evil. It isn't a matter of intellect as much as it is a matter of character. If Scout is not clever to the ways of prejudice and bigotry, then this is a good thing. According to Aunt Alexandra, then, Scout would be considered dull for not understanding her, Alexandra's, prejudices.
She believes that Scout does not have the proper view of society and thus calls her dull. She does not speak or act like a lady should all the time and she does not wear dresses as often as she should. Scour is very smart but when it comes to people bossing her around, she will not have that. She wants to be herself without conforming to something she is not.