The instinctual subtypes or variants add an additional distinction within each of the nine Enneagram personality types. The instincts add a "flavor" to each type that is often used to explain variations that may appear between individuals of the same type. There are two approaches to using the instincts for each type.

With the more traditional approach, each of the nine personality types has three subtypes or variants based on whether the individual has a preference for self-preservation, intimate or social interests (e.g., self-preservation type 1, sexual type 1, social type 1).

A more recent approach, called variant stacking, orders the instincts according to primary, secondary and tertiary preference (e.g., an sp/sx stacking means the individual has a primary preference for the self-preservation instinct, secondary preference for the sexual instinct and a tertiary preference for the social instinct - notice the tertiary preference is generally omitted from the stacking descriptor).

An interesting feature of the instincts is that individuals of different types can appear similar in terms of their instinctual preferences (e.g., a self-preservation type 1 and a self-preservation type 4).