As a person develops spiritually their area of focus changes and evolves over time. Ernest Wood provides an interesting illustration of this shift in focus within his book Concentration: An Approach to Meditation (Page 100):
It is interesting that the two pyramids of development are inverses. The focus of the undeveloped person (Psychical Impulse) is of little influence for the developed individual. Likewise, the Will or Spirit, the dominating aspect of the developed person, is of little consequence to the undeveloped individual.
I believe that most people who are on the spiritual path, or at a minimum those who would take the time to read a spiritual blog such as this one, are at the Mental Nature level or higher. These individuals are mainly intellectual, or driven by the mind, but are beginning to become aware of and trust intuition. They are beginning to realize that there is something other, something beyond the present world of the objective senses and are beginning to key into intuition.
Based on this diagram, I suspect that the Mental Nature corresponds to intellectually minded individuals, the Higher Emotion to those in touch with intuition, at least in part, and the Will or Spirit corresponds to illumination.
This diagram may serve as a useful visual indication for assessing your current position in terms of dominating tendencies and where to focus your efforts concerning spiritual development.
Concentration: An Approach to Meditation may be purchased at the Celestial Source bookstore.