This paper discusses the role of discourse markers (henceforth DMs) also, besides and plus, which are often used in spoken contexts in order to add information or opinions to what has been said earlier. So far the difference in usage among these DMs has been given simply in the terms of register: formal versus informal or spoken versus written. Even in descriptions of English dictionaries, it has been difficult for English language learners to find out how to use these words. The aim of this paper is to explore what the cognitive effect the DMs also, besides and plus have on meanings in a given utterance. I will, focusing on some cases of these DMs seen in movie captions, identify their functional meanings by examining the contexts in the discourse that they are used, what kinds of utterances are used and/or speech acts are performed before and after them, how given information is connected to each other and what the speakers intend to communicate by using these DMs. I will also show the functional difference among these DMs.