If you look back at the circle in the graphic, you will notice something interesting. Finally, Numbers 5, 6, and 7 on the Enneagram tend to approach life through the head/thinking center. Numbers 2, 3 and 4 will process aspects of their life issues from the heart/feeling center. Numbers 8, 9, and 1 tend to approach and react to life through the guti/reaction center.
The triads typically show your reaction or your approach to life. The nine numbers of the Enneagram are divided into three sections, called Triads.