More about collective and individual properties

This short chapter is primarily for those who are fearful of what lies ahead and might be tempted, at this point, to turn back. Except for the title and the last line, g is not mentioned and there is no technical discussion at all. Instead, the aim is to show that the essence of factor analysis is already familiar to us. We do it in an informal way all the time and the purpose of the theory is, simply, to identify the key ideas and to provide the tools to carry the analysis out quantitatively.

We have already made the point that collective properties are familiar in everyday life. It will help us to get to grips with the nature of the factor analysis of mental abilities if we begin here and spend a little more time exploring this relatively familiar territory. Personality was mentioned as an example of a collective property which seems to be rather more than a simple average of a set of personal attributes. Two other, rather simpler, collective properties which lend themselves to the sort of exploratory investigation we wish to undertake are size and shape. These are familiar to all of us and yet they have a good deal in common with the more elusive and contentious matter of intelligence which is our ultimate goal.

Many objects occurring in nature vary in size and shape; pebbles on the beach, apples or, even, octopuses.