Some people say language influences personality, i.e. that the language you use changes the way you behave, and that you might have a different personality when you speak one language than you do when you speak another language. (For example, here is an article making a claim like this.)
Have students discuss whether they think language influences their personality or the way they behave in a way that's related to linguistic relativity. Therefore, they will have to think carefully about what specifically causes their personality to change. (e.g., if someone switching language changes their personality to fit the context—for example, if someone uses English in a professional context and Chinese at home—that would not be evidence for linguistic relativity.) If language and personality are related in a way that's about linguistic relativity, there would need to be evidence for someone's personality changing because of specific grammatical features of the language they are speaking.