Measurement structures and psychological laws.

Empirical laws psychology may be based on physical measurements (for example, voltages, times), counting, ordering, or just classifying. It is a pointless, though widespread practice to use a physical measure or a count as a "definition" of a psychological variable; this practice obscures the fact that all one has done is measured a physical variable, or counted. What is important are the empirical laws that are established by use of such quantitative or qualitative observations. Some kinds of empirical relations and laws yield measurement structures, akin to the qualitative structures underlying fundamental measurement in physics. Measurement structures are empirical structures that can be described most simply by introduction of a new numerical function; such a function is a new measure, and is typically interpreted as measuring some particular psychological variable Measurement structures, formulated abstractly, sometimes provide valuable tools for formulating new empirical hypotheses to be tested; but in many instances, other kinds of theory may be more appropriate. The main focus of research ought always to be the discovery of simple laws; these may or may not lead to new measures.