The heart triad, also called the feeling or image triad, comprises types Two, Three and Four, and the emotion the system assigns to it is shame. The three are held to handle it differently: Two seeks worth through being needed by others, Three through achievement and the image of success, and Four through the cultivation of a distinctive identity, with Three at the centre regarded as the most out of contact with the underlying feeling. The triad's concern is with identity and with how one appears, and its time orientation is the past. Naming shame rather than sadness as the core affect is one of the points where the modern Enneagram draws on twentieth-century psychology rather than on any older source, and the debt to the character theory of Karen Horney is explicit in Naranjo.
The heart triad also splits, rather than groups, on Riso and Hudson's second system, the Hornevian groups, drawn from Karen Horney's three neurotic trends and set out in The Wisdom of the Enneagram (1999): Two falls among the compliant types that move toward others, Three among the assertive types that move against, and Four among the withdrawn types that move away. Every triad of three adjacent points on the circle turns out, on this second scheme, to contain one member of each Hornevian group, since the two classifications were built to measure different things, one a shared core feeling, the other a shared interpersonal strategy, and were never meant to align.
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