In social science an psychometrics, construct validity refers to whether a scale measures or correlates with a theorized psychological construct (such as "fluid intelligence"). It is related to the theoretical ideas behind the personality trait under consideration; a non-existent concept in the physical sense may be suggested as a method of organising how personality can be viewed. The unobservable idea of a unidimensional easier-to-harder dimension must be "constructed" in the words of human language and graphics.