The audience and intentions of a research paper decide the tone. If your essay is going to be printed in a scholarly or didactic publication or reviewed by a college professor, a formal and succinct tone is best. Writing for a more leisurely and laid back audience calls for a more casual and conversational tone.
Scientific research essays are written with brevity, authority, and precision because they usually include statistics, numbers and data. Most scientific papers are written in the American Chemical Society style, which provides guidelines for using numbers, tables, graphs and figures.
The Modern Language Association style is the most common style used for research essays in college. The MLA style formats how to cite sources of information both in the body of your essay, footnotes, endnotes and at the end in a bibliography.
The American Psychological Association style is another style commonly used in college research essays, but is seen more in upper-level and graduate level classes and in social science essays. As with the MLA style, it guides writers on how to cite sources of information, but has a different format than the MLA style.
The Chicago Manual of Style is primarily used by editors, but can also be used in research essays for documenting sources and for grammatical usage. The CMS style is used for essays in literature, history, the arts and the social sciences.