The Enneagram instincts are not represented on the Enneagram symbol itself. The three instincts are the self-preservation instinct (abbreviated sp), the sexual or intimate or one-to-one instinct (abbreviated sx), and the social instinct (abbreviated so or soc). The three instincts were originally used with the personality types to create three subtypes or variations of each type. For example, a type 1 can be one of three subtypes.

• a self-preservation 1 (abbreviated sp 1)
• a sexual 1 (abbreviated sx 1)
• a social 1 (abbreviated so 1 or soc 1)

While all three subtypes are still type 1, they are each preoccupied with a different instinct. The goal with the instinctual subtypes is not simply to identify which of the nine types are a best fit for an individual, but to identify which of the twenty-seven subtypes are a best fit.

A more recent approach to the instincts determines a preferential order to all three instincts. Rather than only looking at one instinct an individual determines which instinct is most preferred, secondarily preferred, and least preferred. This preferential or stacking approach can also be used independent of Enneagram type (e.g., two people with the same stacking are compared without regard to Enneagram type). When used with type, instinctual stacking produces six variations for each type. The shorthand used to represent stacking includes the primary and secondary instincts but the tertiary or least preferred instinct is omitted and assumed (e.g., sp/sx where the social last instinct is omitted). As an example, the six instinctual stackings or variants for type 1 are:

• sp/sx 1: self-preservation 1st, sexual 2nd, and social 3rd
• sp/so 1: self-preservation 1st, social 2nd, and sexual 3rd
• sx/sp 1: sexual 1st, self-preservation 2nd, and social 3rd
• sx/so 1: sexual 1st, social 2nd, and self-preservation 3rd
• so/sp 1: social 1st, self-preservation 2nd, and sexual 3rd
• so/sx 1: social 1st, sexual 2nd, and self-preservation 3rd

Here's a free test to help determine Instinctual Stacking or Variant.