Towards the end of the summer, Nana quite upset the household. She was six years old and promised to be a thorough good-for-nothing. So as not to have her always under her feet her mother took her every morning to a little school in the Rue Polonceau kept by Mademoiselle Josse. She fastened her playfellows' dresses together behind, she filled the school-mistress's snuff-box with ashes, and invented other tricks much less decent which could not be mentioned. Twice Mademoiselle Josse expelled her and then took her back again so as not to lose the six francs a month. Directly lessons were over Nana avenged herself for having been kept in by making an infernal noise under the porch and in the courtyard where the ironers, whose ears could not stand the racket, sent her to play.

[…]

Boche said that children pushed up out of poverty like mushrooms out of manure. All day long his wife was screaming at them and chasing them with her broom. Finally she had to lock the door of the cellar when she learned from Pauline that Nana was playing doctor down there in the dark, viciously finding pleasure in applying remedies to the others by beating them with sticks.

In this excerpt from L'Assommoir, the narrator describes Nana's chaotic childhood in the slums. This is the same Nana who is the heroine (or rather the anti-heroine) of Zola's novel Nana. This little girl is going to end up dead with a pustule-covered face. Dang.

In this excerpt from Zola's novel, we can the see the narrator making links between Nana's social environment and her character. Nana is a child of the slums. She is a child of poverty, and the chaos in which she grows up is reflected in her character.

Her mother puts her in Mademoiselle Josse's school "so as not to always have her under her feet." Her mother doesn't have time for her, in other words. At Mademoiselle Josse's school, Nana runs wild, because clearly Mademoiselle Josse is incapable of disciplining her. So Nana's social environment isn't the best for a child. And this environment has a really bad effect on her character… and directly leads her into a life of prostitution.

The relationship between social environment and character is encapsulated in Boche's statement that "children pushed up out of poverty like mushrooms out of manure."

This statement pretty much sums up the Naturalist view of social environment. People push up out of their social environments like plants. In other words, they absorb from their social environment whatever is there, in the same way that a mushroom or any other plant absorbs whatever is in the soil that feeds it. Bleak? Sure is.