Gilman uses the figurative language like imagery, similes, and personification. The purpose is to achieve the effect of a woman being out of touch with reality.
Detailed answer:
Imagery or sensory language describes objects and surroundings. Gilman writes, “The color is repellant, almost revolting; a smoldering, unclean yellow, strangely faded by the slow-turning sunlight.” Many adjectives and adverbs present the physical state of the wallpaper. The woman’s emotions in relation to the walls are also put in detail.
A simile is a figure of speech that compares one object to another for descriptive purposes. The author describes the wallpaper, “the outside pattern is a florid arabesque, reminding one of a fungus. If you can imagine a toadstool in joints, an interminable string of toadstools, budding and sprouting in endless convolutions.” The wallpaper pattern is compared to the string of poisonous mushrooms (“toadstool in joints”). It contributes to the disgusting imagery and forms toxic connections in the reader’s mind.
Personification attributes human-like or natural traits to a non-living object. There is a perfect example of this in the story, “It slaps you in the face, knocks you down, and tramples upon you. It is like a bad dream.” The narrator describes the torture caused by watching the wallpaper. She compares it with human violence. Bonus point – the last sentence, “it is like a bad dream,” is also a simile!