The measurement of intelligence
We doubt that any expert in psychological measurement would state that the measures they develop or use capture every aspect of the psychological concepts they are investigating. Human behaviour is extremely complex to understand and to measure. One of the main problems that psychologists continually face is that the things they wish to understand are not always directly observable and therefore measuring them becomes problematic. This is in contrast to disciplines such as biology, where the biologist can name, measure and count different cells or organisms. Thus, the perennial problems of psychology can be stated as (a) defining unobservable concepts and (b) measuring unobservable concepts. Take, for example, the concept of jealousy. How would you define it? What is jealousy composed of, and how would you measure it? Sure, we all think we know what jealousy is, and perhaps have had a personal experience of it, but when it comes to defining what it is, then it becomes a much more difficult task. For the psychologist then, the problem is to ascertain a set of meanings as to what jealousy is, and to then devise ways of measuring these meanings. Again, this is no simple task. Straight away you can see that there are many things that the psychologist needs to consider before any measure can be built. As human behaviours, interactions and attitudes are complex things, any decisions as to how best to represent these are fraught with difficulty and controversy. Decisions as to what the set of meanings for intelligence will include need to be justified, tested and defended. This involves the processes of research.