Descriptive Science A recent Guest Commentary from Infection and Immunity provides some insights on descriptive versus hypothesis-driven research

T he Instructions to Authors for Infection and Immunity state that “IAI will not consider papers that are . . . purely descriptive.” When applied to science, the word “descriptive” has acquired dismissive or pejorative connotations and is frequently provided as justification for rejection of a manuscript or grant application. Given the widespread use of this adjective and its profound implications, it is worthwhile to reflect on what is right or wrong with descriptive science. The word “descriptive” is defined as “referring to, constituting or grounded in matters of observation or experience” (Merriam-Webster online dictionary, http://www.merriam -webster .com/dictionary/descriptive.). Since practically all laboratory-based biological science is based on recording evidence from experimentation, it might be argued that all science is in some sense “descriptive.” However, scientists distinguish between “descriptive research,” in which information is collected without a particular question in mind, and “hypothesis-driven research,” designed to test a specific explanation for a phenomenon. In this dichotomy, “descriptive” has numerous synonyms, including “observational,” “inductive,” or “fishing expedition,” while “hypothesis driven” may also be referred to as “hypothetico-deductive” or “mechanistic.” When scientists favor hypothesis-driven science over descriptive science, they are really saying that they prefer work that is explanatory or provides insights into causation. In considering this issue, it is noteworthy that many esteemed scientific disciplines, such as astronomy, archaeology, and paleontology, are almost entirely descriptive sciences (D. A. Grimaldi and M. S. Engel, Bioscience 57:646–647, 2008). Newton’s laws of motion can be considered descriptive, and there is nothing mechanistic about the gravitational constant. Nevertheless, we hold these laws in great esteem because they are able to predict the behavior of the natural world. One cannot perform an experiment in which a stellar variable or a geological epoch is altered. Moreover, the descriptive sciences of taxonomy, anatomy, botany, and paleontology have been central to the development of evolutionary theory, which remains the linchpin of all biological sciences. Hence, there is nothing fundamentally wrong with descriptive research, with the caveat that a scientific field may demand more from an investigator once it becomes an experimental science. In microbiology and related medical sciences, the transition from descriptive research to hypothesis-driven research has generally reflected the maturation of these fields. In the early stages of a field, descriptive studies may “represent the first scientific toe in the water” (D. A. Grimes and K. F. Schulz, Lancet 359:145–149, 2002). Initial observation and induction give rise to novel hypotheses, which subsequently can be experimentally tested to provide a progressively detailed mechanistic understanding. Specific hypotheses allow a more discerning interrogation of complex data sets, something recognized by Darwin when he noted, “Without speculation there is no good and original observation” [C. F. Darwin, F. Burkhardt (ed.), and S. Smith (ed.), The correspondence of Charles Darwin. Cambridge University Press, Cambridge, United Kingdom, 1985). On the other hand, a descriptive approach may be less prone to bias (F. M. Marincola, J. Translat. Med. 5:21, 2007). “It is Arturo Casadevall is Chair of the Department of Microbiology & Immunology Leo and Julia Forchheimer Chair in Microbiology & Immunology and Professor in the Department of Medicine, Albert Einstein College of Medicine, Bronx, N.Y., and Ferric C. Fang is Professor of Laboratory Medicine and Microbiology, University of Washington School of Medicine, Seattle. This article was originally published in Infection and Immunity 76:3835– 3836, September 2008.