that g is not a mental or cognitive process or one of the operating principles of the mind, such as perception, learning, or memory. Every kind of cognitive performance depends upon the operation of some integrated set of processes in the brain. These can be called cognitive processes, information processes, or neural processes. Presumably their operation involves many complex design features of the brain and its neural processes. But these features are not what g (or any other psychometric factor) is about. Rather, g only reflects some part of the individual differences in mental abilities (as defined in Chapter 2) that undoubtedly depend on the operation of neural processes in the brain. By inference, g also reflects individual differences in the speed, or efficiency, or capacity of these operations. But g is not these operations themselves.
A simple distinction between process and factor is that a process could be discovered by observing one person, whereas a factor could be discovered only by observing a number of persons. For example, one person is observed throwing darts at a target, trying on each trial to hit the bull's-eye. In the course of fifty trials, the person gradually improves in his level of proficiency, from at first being able to hit the bull's-eye only once in every ten trials to finally hitting the bull's-eye on nine out of every ten trials. This observable change in the person's level of proficiency over the course of practice represents a process, in this case learning. Many of its characteristics could be discovered by means of experiments on a single person. (In fact, Ebbinghaus discovered some of the basic facts of learning and memory by experiments using only himself as a subject.) But now we observe another person performing the same dart-throwing task. We see that it takes this person 200 trials to attain the same level of proficiency as was attained by the first person in only fifty trials. So here we see individual differences in the process of learning, in this case, a difference in the rate of learning. Obviously, this discovery that learning rates for this task can differ could only have been discovered by observing more than one individual. We could then devise several other diverse tasks in which learning (i.e., improvement with practice) can be seen to occur. We may then find that on every task these two persons differ consistently in their rate of learning. If so, this would mean that all the tasks are positively correlated. At this point, a factor, call it "general learning ability," has been discovered. Simply stated, we have demonstrated the existence of a single dimension of individual differences that cuts across a variety of learning tasks.
|Principal components analysis. The first principal component (PC1) in a principal|