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Despite the controversy over the problems of relying on empirical data in Psychology, I think that it is the only way to find answers to many fascinating questions about humans. The patterns of data can tell us things that we have no other access to without empirical research. It is critically important for people to be aware of the limitations and problems, but then to go on and collect the data.

—Laura Edelman, Professor of Psychology

EXPERIMENTAL EVIDENCE

Experimental evidence is a form of empirical evidence. Empirical evidence is derived from experience, the result of observation and experiment, as opposed to theory. It is usually associated with the bodily senses; the word empirical means “capable of being observed, available to the senses,” and the word comes from the Greek word for experience.

Experimental evidence is usefully distinguished from other forms of evidence by the careful attention to procedure it requires. Evidence in the sciences is usually recorded in particular predetermined formats, both because of the importance of methodology, and because the primary test of validity in the sciences is that the experiment must be repeatable, so that another experimenter can follow the same procedure and achieve the same results (see Chapter 15, Forms and Formats Across the Curriculum).

The concern with procedure is present throughout writing in the sciences, though, not just in the Methods section of a lab report. Scientific writing constantly begins by asking the question, “How do we know what we think we know?” And, since experiments inevitably take a scientist into the unknown, it then asks, “On the basis of what we know, what else might be true, and how can we find out?” The concern with procedure in scientific writing is ultimately, then, a matter of clearly articulating the means of verifying and explaining what we think we know.

The treatment of evidence in the following example of scientific writing, a review of existing research on a given phenomenon, explores the adequacy of competing hypotheses.

Excerpt from “Hypotheses about Rev Function”

Two major hypotheses for Rev function have been proposed. One is that Rev may inhibit splicing or interfere with the assembly of the spliceosome. This hypothesis would imply that inhibiting spliceosome activity would release pre-mRNA for transport to the cytoplasm (Fischer et al. 1995). The other hypothesis is that Rev might directly target viral pre-mRNA to the cytoplasm through the interaction of its domains with cellular cofactors. [States hypotheses and their implications] While there is evidence to support both models, there seems to be stronger support in favor of the second hypothesis. The finding that functional inactivation of the Rev activation domain always resulted in the inability of the protein to exit the nucleus provides significant evidence that the activation domain is a nuclear export signal (NES) and Rev is indeed actively involved in the direct transport of viral mRNAs (Meyer et al. 1996). [Offers as rationale for preferred hypothesis that it better explains evidence] Additionally, Rev was able to directly promote nuclear export of RRE-containing mRNAs after nuclear injection into Xenopus oocytes independently of the presence of introns in these RNAs and thus presumably in the absence of spliceosome formation (Fischer et al. 1994). [Adds additional evidence from second source to support preferred hypothesis]

USING AUTHORITIES AS EVIDENCE

A common way of establishing support for a claim is to invoke an authority—to call in as evidence the thinking of an expert in the subject area you are writing about. The practice of invoking authorities as evidence can be heard in TV advertising (“three out of four doctors recommend…,” etc.) as well as in scholarly books and articles, where a writer may offer as partial support for a claim the thinking of a better-known writer. Much academic writing consists of evaluating