Testable hypotheses  (by Dan Reisberg, ch. 1)

Research in cognitive psychology can yield results that are both important and useful. These results have value, however, only if they are based on sound methods and good science. If not, we may be offering practical suggestions that do more harm than good, and theoretical claims that lead us away from the truth, not toward it.

For students learning about cognitive psychology, therefore, it is important to understand the methods that make our science possible. This will allow them to see why our results must be taken seriously, and why we can, with confidence, draw the conclusions that we do. For this reason, I have written a brief methods essay, highlighting a methodological issue or focusing on a research example, for each of the chapters in the text. I hope these essays will help convey why our methods are as they are, and help students understand more fully how our science proceeds.

First, though, we might ask: What is science, and what is it about cognitive psychology that makes it count as a science? One key lies in the testability of our claims: In order for psychology to be a science, our claims must rest on a basis that's more solid than mere opinion, or interpretation, or argument. We need our claims, instead, to rest on the facts, and that means we need a way to check each assertion against the facts, to find out with certainty whether the assertion is correct or not. Then, if we learn that an assertion does not fit with the facts, we are obligated to set it aside, to make sure that we offer only claims that are supported by good evidence.

How does this testing of hypotheses proceed? The answer has many parts, but one idea is crucial: Scientific hypotheses need to be framed from the start in terms that make the testing possible. That means we must avoid vague or ambiguous terms, so that it is obvious what facts fit with the claims and what facts do not. Otherwise, we'll have no way of making certain that our claims are well founded.

Even when we have a relatively specific hypothesis, we need to define our terms with care. For example, consider the claim: "No matter what day of the year you pick, someone famous was born on that day." Is this hypothesis correct? Imagine that the most prominent person you can think of, born on December 19, is Daniel Reisberg. Does this confirm the claim, because Reisberg is famous? (After all, many thousands of students have read his books.) Or does it contradict the claim, because Reisberg isn't famous? (After all, most people have never heard of him.) Both of these positions seem sensible, and so it will be a matter of opinion whether our observation about December 19 fits with the claim about birthdays or not. Hence the truth of the claim about birthdays depends on opinion, not fact, and so the claim is not testable. To make it testable, we'd need to find a suitable definition of "famous." Only then could we say if our observation about Reisberg fits with the hypothesis or not.

This example illustrates, therefore, why a scientific hypothesis must be framed precisely-so that we can check the facts, and then say with certainty whether the hypothesis is correct. But how do we "check the facts"? We'll explore this in upcoming methods essays.