In his early research, he isolated 16 personality factors, which he composed into a test called, of course, the 16PF!
Later research added seven more factors to the list. Even later research added twelve “pathological” factors found using items from the MMPI (Minnesota Multiphasic Personality Inventory).
A “second order” factor analysis on the total of 35 factors revealed eight “deeper” factors, as follows, in order of strength:
1. Emotionality-impassiveness: How emotional and excitable were the babies? Some were given to emotional outbursts of distress, fear, and anger -- others were not. This was their strongest temperament dimension.
2. Sociability-detachment: How much did the babies enjoy, or avoid, contact and interaction with people. Some babies are “people people,” others are “loners.”
3. Activity-lethargy: How vigorous, how active, how energetic were the babies? Just like adults, some babies are always on the move, fidgety, busy -- and some are not.
4. Impulsivity-deliberateness: How quickly did the babies “change gears,” move from one interest to another? Some people quickly act upon their urges, others are more careful and deliberate.
The last one is the weakest of the four, and in the original research showed up only in boys. That doesn’t mean girls can’t be impulsive or deliberate -- only that they seemed to learn their style, while boys seem to come one way or the other straight from the womb. But their later research found the dimension in girls as well, just not quite so strongly. It is interesting that impulse problem such as hyperactivity and attention deficit are more common among boys than girls, as if to show that, while girls can be taught to sit still and pay attention, some boys cannot.
In the last couple of decades, an increasing number of theorists and researchers have come to the conclusion that five is the “magic number” for temperament dimensions. The first version, called The Big Five, was introduced in 1963 by Warren Norman. It was a fresh reworking of an Air Force technical report by E. C. Tuppes and R. E. Christal, who in turn had done a re-evaluation of Cattell’s original 16 Personality Factors research.
But it wasn’t until R. R. McCrae and P. T. Costa, Jr., presented their version, called The Five Factor Theory, in 1990, that the idea realy took hold of the individual differences research community. When they introduced the NEO Personality Inventory, many people felt, and continue to feel, that we’d finally hit the motherload!