John has only one or two distinct traits and does not change in the story. He always think he loves his wife, but his ignorance and insensitivity eventually drives his wife crazy.
When the narrator is forced to stay in this room day and night, she further observes that a woman is trapped behind the wallpaper. she notices immediately the barred windows but also "disgusting" wallpaper.
When john makes the final decision for his wife and whats best for her and how he think locking her up will be the best decision to help with her postpartum depression.