Art Nouveau and Psychedelic art are similar in using the language of abstract. Both of them are quite in depth of detail, and they are modern art movement. However, there are huge different in art Nouveau and Psychedelic art:

- Psychedelic art use a lot colors which are quite very contrast to each other (in my opinion they sometimes hurt). Those color make very strong impact on viewer. Psychedelic art also use "fractal" patterns quite a lot. Psychedelic art cause confusion on its audience by its pattern and color. The visual effect of Psychedelic art offer its audience an visual experience like they are using Drug. (Psychedelic is a kind of very strong drug, I think this is the reason why this art movement claim such a name)

- Art Nouveau Has notable rhythm. Art Nouveau has repeat pattern, but unlike Psychedelic art art Nouveau don't have fractal/geometric pattern. Art Nouveau painting does not use very high contrast color like Psychedelic art either (since it is influenced by Pre-Raphaelite)