The body triad, also called the gut or instinctive triad, comprises types Eight, Nine and One, the three points at the top of the figure, and the emotion the system assigns to it is anger. The three are held to handle that anger differently: Eight expresses it outwardly and at once, One turns it inward as resentment and self-correction, and Nine suppresses it and often does not know it is there. The triad's underlying concern is with autonomy, control and the boundary between the self and the world, and its characteristic time orientation is the present. The threefold grouping is part of Claudio Naranjo's elaboration of Ichazo's scheme and draws on the older idea, found in Gurdjieff and behind him in a long line of tripartite psychologies, that a person functions through three centres, moving, feeling and thinking.
The three triads are not the only cross-cutting grouping the later literature offers. Riso and Hudson's The Wisdom of the Enneagram (1999) proposes a second system, the Hornevian groups, drawn from Karen Horney's three neurotic trends of moving toward, against and away from other people; on that scheme the body triad splits rather than groups together, Eight falling among the assertive types that move against, One among the compliant types that move toward, and Nine among the withdrawn types that move away. The two schemes measure different things, the emotional triads a shared core feeling, the Hornevian groups a shared interpersonal strategy, and a given type belongs to one of each.
Sources The Enneagram: G. I. Gurdjieff's Esoteric SymbolCarole M. Cusack with Personality Types: Using the Enneagram for Self-DiscoveryDon Richard Riso and Russ Hudson