When it comes to emotive language, I stumbled upon the famous Sapir-Whorf hypothesis. You can read all about it here. This hypothesis claims that the language we speak shapes the way we think.
Also, I found a study on how Spanish-English bilinguals speak Spanish in a more emotional tone than they do English, regardless of their nationality (unfortunately I cannot remember where did I find it, I'll quote it here later).
That's interesting enough, but the problem is how do I relate it to ESL classrooms in Malaysia? Maybe a bit more reading would help (which I still am yet to do until now so sorry Dr. T.T) so I Googled some more.
I also found another theory that can be the base of my research: the framing effect. This theory believes that the way we speak/construct our sentences affect people's decision-making, which sounds a lot like persuasive speech. The effects of framing, based on my little bit of reading, were frequently researched on in the field of politics and marketing, but not education.
If you are interested to know more about framing effect, this website has a number of amusing examples. :)
When it comes to framing effect, I was thinking that I could relate to how we can teach persuasive speech/essay to ESL learners. Other than that, I could relate the emotions found in language with literature. When I discussed this with my friends, they also suggested that I could research on the way teachers construct their reinforcements to students. As you may have already known, B. F. Skinner proposed that there are two ways to shape learner's behavior, that is via positive reinforcement and negative reinforcement. This is one of the basis of behaviorism.
All in all, there's just too many concerns which strike my fancy. I might draw a problem tree later on. Also, I have yet to think about the 3Cs that Dr. has told us to: concern, context, and corroboration. I'll come back here once I've refined my research topic.
Till then! :D