INDIVIDUAL AND GROUP DIFFERENCES
Individual differences are primary; group differences are secondary. The individual is the biological and societal unit that develops, that learns, that thinks, that wants, that feels, that acts. The group is a collection of individuals – sometimes just that, sometimes with a structure of its own.
The individual members of any species, such as humans, have a great many characteristics in common; indeed, judged against the varied forms of life on this earth one might deem them virtually indistinguishable. Yet from a viewpoint within the human species, we see them as differing in an array of biological and psychological characteristics, and these differences are often of intense social, personal, and economic interest to us.
On the basis of such individual variation, individuals may be classified in numerous ways and for various purposes into subgroups. A particular human may be placed simultaneously into groups according to age, sex, occupation, ancestry, religious preference, marital status, home ownership, political party affiliation, sexual orientation, television viewing habits, taste in soft drinks, and any number of other criteria. These classifications can be said to be secondary in the sense that they derive from already-existing characteristics of the individual; that someone may choose to classify an individual into one or another category does not in itself change that individual in any way whatsoever – although, of course, the individual's or others' reactions to this act of classification may have such an effect.