Independent variables are variables that scientists and researchers use to predict certain traits or phenomena. For example, intelligence researchers use the independent variable IQ to predict many things about people of different IQ levels, such as salary, profession and success in school. However, one important fact that researchers must take into account before designing and performing research is there are essential differences between types of independent variables. Researchers divide independent variables into the categories, “operational” and “conceptual."

A conceptual independent variable is one that a researcher may “think up” or conceptualize prior to performing a study. The conceptual independent variable is the one that the researcher truly wants to measure. For example, intelligence researchers are interested in the “g-factor,” which is a theoretical psychological mechanism that allows humans to solve novel problems.

An operational independent variable, on the other hand, is one that the researcher uses in her study. For example, a researcher interested in measuring a person’s IQ may administer a Raven’s Matrices IQ test; in this case the operational independent variable is an individual’s score on this test.

Conceptual and operational independent variables arose in different manners. A conceptual independent variable can be one that the researcher personally invents and defines, such as “taste in music,” or one that exists in scientific literature, such as “gratitude.” Operational independent variables are different in that they arise from issues of research design. For example, it may not be possible or efficient to measure something abstract like “gratitude.” In such a situation, issues of convenience and practicality give rise to an operational independent variable that can be easily measured.

Conceptual independent variables are the “ideal” in that they are what the researchers are sincerely interested in. However, in real studies, it is often impossible to measure such a variable. For example, you cannot directly measure a psychological mechanism such as the g-factor. Thus in terms of measurability, conceptual and operational independent variables differ in that operational is measureable and conceptual is not.

Operational variables are extremely specific to the extent that they can be measured and reported without misinterpretation. Reaction speed on a memory recall task is specific in that in can be measured in objective terms, such as seconds. On the other hand, conceptual variables are subject to different interpretations. Terms like “intelligence” and “gratitude” may mean different things to different researchers, making conceptual variables the subject of scientific debate.